It's not quite an RV, but when our oldest kid was 3 months old we looked at each other and said "how are we going to get out into the mountains and desert?", and purchased a VW Eurovan. From a dealer, who wasn't negotiating. I still think it was a good purchase:
We paid cash (which we had)
They had just increased the engine to a V6, and since we both had jobs with limited vacation time, the V4 "you can just push it uphill" version didn't make sense if we actually wanted to get places. This one easily does 70 uphill over the mountains. So used wasn't really an option.
it allowed us to easily keep camping with babies, small kids, and medium-sized kids, and then mostly became a vehicle that we use to go skiing, both backcountry and at small areas where we could just go back to the (nearby) car and spread out at the table for lunch. It's really nice to all be able to put on ski boots (comfortably) inside the vehicle! So transportation for 16 years of 2X/year backcountry hut trips.
We got to take many trips with the kids to the wild canyon country in Eastern Utah: having the van meant we could get there (it's not 4wd or especially high clearance, but we got it down many a not-too-crazy 4wd road, and carried shovels and jacks and such), head way out into the unimproved protected area, have a place to hang out if it rained, or got horrifically buggy. I know people CAN do these kinds of trips without the van setup, but it hit the sweet spot for us between being able to just ... get up and go on fairly short notice. We know how everything got packed, if the weather was iffy for a few hours we could just all read inside, and it was a way to clean up small kids before meals and expect them to stay clean for 5 minutes.
One of our kids didn't ride well in cars: on this it was really easy to pop the top and set up the beds if we'd started driving after dinner (have dinner, put on his PJs, put him in the car seat, go) and were just too tired to continue (there's a great stopping point about 5 hours form our house).
As the kids got older, we stuck a bike rack on the back to increase our hiking range on sketchy roads.
The thing is now 21, and mostly sitting in the driveway while we think about what to do next: the transmission is coming up on needing replacing, so we're considering our options. The thing is, it's not particularly high-profile (which means it's fairly easy to drive in heavy cross-winds, unlike sprinters and such), it gets 20 MPG (which we consider embarrassingly bad, but it's better than almost any current equivalents out there) and it's pretty low-mileage at this point, and we know all the maintenance history.
If we decide to sell it, we can probably get back a significant fraction of the initial cost, which is crazy!
All in all, I'm pretty sure it was $ well spent.