I've had good experiences using a West Coast drawer manufacturer to build custom size drawer boxes. There are also a couple of suppliers on the East Coast that do the same thing for approximately the same price.
Drawer Box Systems, Inc.The price is comparable to purchasing ready-made. Both construction quality and materials are top-notch - solid maple wood, dovetail construction, plywood bottoms for about $25 per drawer, delivered, assembled, and finished with two-part clear epoxy coating. I briefly considered building them myself, but when I priced out the maple, it would've cost me over $300 for the lumber alone versus $220 to have all seven drawers built.
Naturally, price varies somewhat with both width, height, and depth. There are also many design and construction options from which to choose (e.g., cutouts, rounded top, bottom inset, etc.), most of which do not affect price. DBS is set up primarily for building custom drawers for furniture manufacturers, so figuring out how/what to order may seem a bit daunting. Also, you have to set up an account with them before you can order. This may take 2-3 days before you're approved - longer than it took them to actually build me the boxes (less than two days).