They retail for around $9-10 each and are usually found cheaper if you buy in bulk. I got four at a train show for $35, so that is $8.75 each. Bowser offers so many road numbers for each paint scheme that you will probably never need to do any renumbering for this class.
Below is a Dean Heacock pic of a 100ton hopper.
Bowser hoppers are so good, all you have to do is assemble and weather them. I usually give my predecessor ones a good overspray of dark grey followed by a tan on the bottom 1/4 of the car. The Chessie ones I try to keep the weathering lighter since they are most likely newly painted.
Below are several pictures of my cars. I
have 11 C&O, 2 B&O, 1 Chessie C&O, and 1 Chessie
I won't bore you by posting all the pics again. If you
want to see
them all they are on the freight cars page. The two
are pictured with the McKean hopper topper. These plastic
put on cars to turn them into temporary covered hoppers. I
seen Chessie painted cars with "hopper toppers".