If you're not looking for anything fancy and a plain white bakery box will do, then one of the best places to go would be Honeymoonpaper.com. Granted you can't order just 10 boxes, but their prices are way lower than BRP. Most boxes come in bundles of 100 and you can get 10 x 10 x 5 boxes, for example, for like .25 each. I get a lot of 6 x 6 x 2.5 boxes, which 4 cupcakes fit into perfectly, for less than .10 each.
When you go through tons of boxes like we do, boxes prices become very important to your bottom line. Restaurant Depot is also a good place for bulk boxes if you have one near you