As a simplistic analysis, count up all the days you spend on the road (hotels + car rental), and compare that to the cost of a van setup + wear-n-tear. (exclude gas, since that's the same across the two). Then guestimate the number of days you would spend on the road.
As a more complicated analysis, if you're going to try to sell the vanlife van after a period of camping, how much can you get out of it? This starts to be amortization compared to rent. So the various options that can be compared to each other are:
From what I've read, it's incredibly hard to get financing to buy a vanlife van. You might be able to get the base vehicle financed, but not the build-out. So plan on paying cash for that. Also, selling it might be difficult, as a potential buyer may want a different build than you?
The Estes Park solution is looking mighty good.