Since the cruises are pretty much all inclusive (booze, a night at Palo's, and excursions being the exceptions),
for me, this is how I make the comparison:
Cash price to cruise
vs
Number of points needed to cruise
vs
Amount of relative value (which will vary) of our points.
My relative value would change based on how I use, or am willing to use, my points. If willing to rent, the $10 per point value is perfectly realistic.
If I'm not willing to rent, it's completely plausable to assign "yearly dues per point + point cost (broken down by year)". What that means to me is this:
Say you paid $96 per point for 50 years (you bought AKV at first offering) of points AND your annual dues for this year were 4.50 per point.
You might consider your effective value to be (96/50)+4.50 = $6.42 per point.
There is ONE other consideration in there, and CarolAnn mentions it. That is a sort of opportunity cost. If you have finite vacation time (and just about everyone does) and you have to CHOOSE to "use or lose" your points during that time...that is going to be a factor in deciding what route to take. Especially when you have LARGE amounts of points..the banking rules can still cause you fits in terms of getting use out of all your points before they "expire". We're not at the point where that's a consideration for our family, both in terms of points or limitation in vacation time. YET.
For my comparison, the relatively value of my points seems too high to justify using them to cruise. I can get much better value for my money by paying out of pocket and either using my points at WDW OR renting them out, pocketing the cash, and using it to offset cruise costs. Your mileage may vary.