I am reaching out to the collective wisdom of the Forum because I reached out to DCL via email and the response I got back did not in any way, shape or form answer my questions. I have sent them another email, but they are taking longer than usual to respond and I am hoping with your collective wisdom I may get an answer here faster and perhaps more accurate 
Last fall we (sister and I) sailed on the Fantasy and purchased the on-board length-of-cruise “couples” Rainforest Room Pass. We loved the Room, most especially the heated chairs. I spent a LOT of time on those heated chairs. To be honest, I think I only used the fancy showers of the Room maybe twice (once to try them, the second time because I thought I should since we had the pass...). And the hot tubs two or three times. It was all about the chairs
Did I mention the chairs ?? I even fell asleep on one once or twice. I found it great for cuddling down with my tablet and reading, or just relaxing. The sunsets were pretty spectacular, too (and nicely sheltered from the wind). We used it at least once a day, every day.
Ok, enough about my love for the heated chairs.
My real reason for coming to you.
I got home and I did some math. And I realized that it LOOKS LIKE a person would do better $-wise by just buying enough pre-purchase single day passes to cover off each day than to buy the on board length of cruise pass. I was a little miffed.
This December we are doing a B2B on the Disney Dream: 3 night followed by a 4 night. So I ran the math again. The Rainforest Room (RR) pass numbers come from a September 2015 Navigator (via the DisneyCruiseLineBlog site's Personal Navigator repository: http://disneycruiselineblog.com/personal-navigators/ Thank You!!). Because the last day when everyone gets off the ship the RR is closed to departing guests, that day is not counted. For simplification I am ignoring the automatic 18% gratuity since it is on both prices (and makes the difference higher).
Here goes:
According to recent Navigators, the price of the "Rainforest Deluxe Cruise Pass" for the 3 night Dream is: couples $102 and singles $69. For the 4 night the price is couples $144 singles $101.
To buy before-the-cruise-pre-purchase single day RR passes:
For a 3 night cruise:
$16 x 3 days = $48 and * 2 people = $96
this is still less than the $102 couples price for the onboard pass, and quite a difference from the singles $69 price.
(savings of multiple single days:: $6 from couples; $21 from single)
For a 4 night cruise:
$16 x 4 days = $64 and * 2 people = $128
this is an even bigger amount less than the couples $144 pass and even greater for the singles $101 price.
(savings of multiple single days: $16 from couples; $37 from single)
It appears on the surface that just buying each person 3 and 4 RR single day passes is a cost savings over the "cruise pass".
You would save even more if you were a party of 2 where one person wanted every day and the other person only one or two days and you purchased single day passses accordingly (if my math is correct and confirmed by you guys, we may do this as my sister grumbled something about not wanting the heater chairs... I mean the RR… each day... I must have heard her wrong though!!).
So…
What am I not understanding ?
What is the difference(s) in benefits, functions, etc, between the pre-purchased single day passes and the onboard cruise pass, other than the cost savings of buying single day passes ?
If we pre-purchase multiple single day passes are we guaranteed to be able to use them on the days we want to (i.e. every day) ?? I know with the onboard RR cruise pass you are guaranteed to be able to use the RR whenever you want that the RR is open (unless at a given specific moment they were to hit their legal safe occupancy capacity of course, then you can come back later).
Are there other options ?
The RR cruise pass is a "deluxe" pass. What does "Deluxe" mean ? Is there is a non-deluxe and presumably less expensive cruise pass ? If so, what is the difference between the “deluxe” and “non-deluxe” pass ? What do we ask for to get this less expensive pass instead of the more expensive deluxe pass which is always advertised in the Personal Navigators ?
Thanks for your help in clarifying this mystery and hopefully helping us and others save some $.
SW

Last fall we (sister and I) sailed on the Fantasy and purchased the on-board length-of-cruise “couples” Rainforest Room Pass. We loved the Room, most especially the heated chairs. I spent a LOT of time on those heated chairs. To be honest, I think I only used the fancy showers of the Room maybe twice (once to try them, the second time because I thought I should since we had the pass...). And the hot tubs two or three times. It was all about the chairs

Ok, enough about my love for the heated chairs.
My real reason for coming to you.
I got home and I did some math. And I realized that it LOOKS LIKE a person would do better $-wise by just buying enough pre-purchase single day passes to cover off each day than to buy the on board length of cruise pass. I was a little miffed.
This December we are doing a B2B on the Disney Dream: 3 night followed by a 4 night. So I ran the math again. The Rainforest Room (RR) pass numbers come from a September 2015 Navigator (via the DisneyCruiseLineBlog site's Personal Navigator repository: http://disneycruiselineblog.com/personal-navigators/ Thank You!!). Because the last day when everyone gets off the ship the RR is closed to departing guests, that day is not counted. For simplification I am ignoring the automatic 18% gratuity since it is on both prices (and makes the difference higher).
Here goes:
According to recent Navigators, the price of the "Rainforest Deluxe Cruise Pass" for the 3 night Dream is: couples $102 and singles $69. For the 4 night the price is couples $144 singles $101.
To buy before-the-cruise-pre-purchase single day RR passes:
For a 3 night cruise:
$16 x 3 days = $48 and * 2 people = $96
this is still less than the $102 couples price for the onboard pass, and quite a difference from the singles $69 price.
(savings of multiple single days:: $6 from couples; $21 from single)
For a 4 night cruise:
$16 x 4 days = $64 and * 2 people = $128
this is an even bigger amount less than the couples $144 pass and even greater for the singles $101 price.
(savings of multiple single days: $16 from couples; $37 from single)
It appears on the surface that just buying each person 3 and 4 RR single day passes is a cost savings over the "cruise pass".
You would save even more if you were a party of 2 where one person wanted every day and the other person only one or two days and you purchased single day passses accordingly (if my math is correct and confirmed by you guys, we may do this as my sister grumbled something about not wanting the heater chairs... I mean the RR… each day... I must have heard her wrong though!!).
So…
What am I not understanding ?
What is the difference(s) in benefits, functions, etc, between the pre-purchased single day passes and the onboard cruise pass, other than the cost savings of buying single day passes ?
If we pre-purchase multiple single day passes are we guaranteed to be able to use them on the days we want to (i.e. every day) ?? I know with the onboard RR cruise pass you are guaranteed to be able to use the RR whenever you want that the RR is open (unless at a given specific moment they were to hit their legal safe occupancy capacity of course, then you can come back later).
Are there other options ?
The RR cruise pass is a "deluxe" pass. What does "Deluxe" mean ? Is there is a non-deluxe and presumably less expensive cruise pass ? If so, what is the difference between the “deluxe” and “non-deluxe” pass ? What do we ask for to get this less expensive pass instead of the more expensive deluxe pass which is always advertised in the Personal Navigators ?
Thanks for your help in clarifying this mystery and hopefully helping us and others save some $.
SW