It's seems to be a huge park with some workout equipment, a pool, and a few other things, but I think the cost is mainly because of its proximity to Vancouver.
I don't think of it as a huge park--can't say for sure, but I think less than 200 sites. Huge for me are places (Golden Village Palms in Hemet, CA) with over 1000 sites.
The sites are reasonably tight, yet the park is not cramped.
And yes, I'm sure the price reflects proximity to downtown Vancouver. You could try places a little further east (and just off the Trans Canada), but even there I don't think you'll find them that much less than the approx $31Cdn per day at BCRV. Don't forget, tourism is big for Vancouver.
Hope you'll still visit BC; the prices will be lower outside of the urban areas. In Cache Creek, Brookside was $22/day; provincial campgrounds are less, but generally don't have any power and quite often no water.