Stewart hoppers sell in hobby stores for around $8-10 a piece. I found my first one at a train show for $8 and have since found a six-pack for $32 ($5 and change each). I have seen them lately at train shows for $6 each. The six-pack I got was from a hobby shop going out of business, so it was a very lucky find.
The Stewart kits do come with one huge drawback, they don't come with couplers. You will need to buy the Kaydee couplers and attach them yourselves with the small screws supplied in the kits. Add these parts during construction.
Below is a pic of a typical WM 70 ton hopper. Another
Dean Heacock pic. Also a C&O hopper from the exact class the
model represents. John Whitmore took the C&O photo.
Dean Heacock photo John Whitmore photo
Building this kit is fairly straight forward. The only real drawbacks in markings are the lack of consolidated stencils or ACI cards. The kit does come with wheel dot inspection markings, which is nice. You can easily add the missing consolidated stencils during construction.
There is another drawback on the markings of the C&O cars. The Ches-C logo is actually one rib too far to the left. See the pic above of the C&O car and compare it to the model below. The Ches-C logo on the model should be centered on the second rib, not the third from the right.
Below is a pic of two of my Stewart 70 ton hoppers.