I was born in Montana (though don't live there now) and I've been to Yellowstone about 7 times. I've been to Jackson hole, Grand Teton, Gardiner, West Yellowstone and Big Sky. The OP states that her primary concern is about the expense. I will give a number of thoughts which may help the OP consider the value to her, as each person's value proposition can be quite different.
There are a number of situational factors I anticipate would influence value: How many will be travelling? What are there ages? Have you been to the Yellowstone area before? Do you intend to visit the area again to see the things you may miss? How comfortable would you be using the
ABD itinerary as a guide to book your own trip? Do you like the company of a group? How valuable is not driving your self? How valuable is the ABD guide for you?
ABD's YNP/GTNP itineraries are complimentary and tactically smart. Starting from the south in Jackson Hole, the WYOMING itinerary lets you see GTNP, South, South East, and East YNP in a clockwise loop. Starting from the north in Bozeman, The MONTANA itinerary lets you see West, North, and Northwest YNP and the Big Sky area in a clockwise loop. There is a little overlap in the center at Old Faithful. But you'd be OK seeing Old Faithful twice.
*The Yellowstone area is slow driving and it's like solving a puzzle to work out touring plans that don't involve a lot of backtracking.By breaking up the area into two trips starting in different locations, ABD has avoided some of the backtracking - which could add 2 days of nothing but driving if you tried to do this in one trip..
*Staying inside YNP at one (or more) of the historic lodges can avoid a lot of the backtracking to lodging at a gateway town just outside of the park. It can be very difficult to book in the park lodging (for a good selection of dates in the summer you often have to book a year early! - look for cancellations if you are flexible). This ADB Montana itinerary does not include in the park lodging - though they've scoped the itinerary so it is not such an issue as if you were to try to see everything in the park.. The ADB Wyoming trip does include one night at Old Faithful Snow Lodge (and a night at the Wort Hotel in Jackson Hole) - those can be hard to get on shorter notice, which could be of greater value.
*Starting on gateway area winding your way through the park over a couple of days leaving through another gateway area avoids the worse back tracking you'd experience if you chose one base out of the park. Both ADB's Yellowstone itineraries use this strategy, which is good.
*Trying to see everything in the YNP/GTNP area in one week is like trying to race through all of the attractions at WDW in one week It is doable, but it can get to seem like a lot of driving from one point to the next and getting out to look for 30 min and then getting back in the car for another hour. The ABD itineraries builds in quite a few non-sight seeing activities to break up the driving -which I think is really smart.
*All of these types of activities are easily booked by yourself - but this takes time and research. ABD is providing a guide to glue it together.
Bottom line:
*If you prefer to travel on your own you can use the ABD itineraries as inspiration to create 2 similar 1 week trips that carve up the travel in the same strategic way. I think you'd save 50% on a 2 person trip and 66% on a family of 4. The value you are losing DIY is your elbow grease planning, driving yourself, no new friends in the group. For *myself* a domestic trip in my old back yard, I would use the ABD plan but DYI -YMMV.
*If the activities don't matter to you and you just want sight seeing, you can make a 1 week itinerary and see everything and save even more. If you think that you are going to visit this area only once your life, then maybe this is the way to go. For me, I'd recommend breaking it up into 2 trips similar to the way ABD does.
*IF I could do only one, for me I would choose Wyoming. The Tetons and the sections of YNP visited are more spectacular. The Montana itinerary is very worth seeing-but its a notch lower on the spectacular side.
