We did stay at both KOAs (one on each side of Glacier) and you're right, they're pricey. The west side one is much nicer, but a few years ago they cut down almost all the trees - I guess to make those who want their satellite TV to work? Anyway, that was a disappointment to us. That said, we did drive into Mountain Meadow CG and it looked wooded & nice. We'd probably give that a try on a return trip.
The east side of Glacier is not a heavily wooded area; it's where the prairie meets the mountains. Not even a lot of shade in Apgar CG (and of course no hookups). Therefore, you won't find as much choice on the east side. The KOA is well-located, though, quite convenient to the east end of Going to the Sun Road, and to some grocery stores and the visitor center. Didn't check out a lot of other CGs on that side, other than driving thru Apgar.
