It depends on where you shop and what you are buying.

Most of the cheap stuff is not sardines but shad. If you want real sardines look for "bristling" (that means small) on the can otherwise you get a can of shad with 2 or 3 big chunks of fish. True sardines are small, finger sized and are packed 10-12 to a can.

The best I have found so far are:
Crown Prince (from Scotland) - $1.90 can
Bela Olhao (from Portugal) - $1.75 can

Check the ethinic food isle too in the store.