Just as a point of comparison, I put in a mock order to my usual supplier. This is a top-notch vendor and I like its product. Always perfectly done and shipped very securely.
16x20 frame, metal least expensive molding, Alpha rag mat board, acid free backing board, and glass.
12 of them will cost me $380 + 43 shipping from TX to FL.
Doing the same with no glass ends up being $300 + $16 shipping.
So, after all is said and done, your deal was actually decent. Shipping seems excessive but you'll pay that one or the other anyway, either as part of the frame or as S&H. Ordering from outlets like this usually means you'll have a chance to pick and choose.... if you didn't pick something, even accidentally, you aren't going to get it. Very annoying I know but my vendor is similar. It does make it clear what exactly you are ordering several times in the process though.