Don't quote me on this, but I'm pretty sure they return them - at least they do by me. Our Rite Aids, Drug Marts, and Walgreen's typically have their own mini-labs in the store. Just ask before you leave them your film.
Unfortunately for me, our Drug Mart does a good job developing, but their printing is ink; I tried it, but don't like the prints. Our Walgreen's has both ink and RA-4, but their film processing has become too variable.
I've no idea of the prices - I usually don't pay attention to that when having film developed and printed. I usually get the CD, and double-prints (so I can give some away). I'm guessing around $15-$20 a roll with prints and disc.