If you go to a true fastener supply store they are a lot cheaper than buying them from a hardware store or someplace like Lowes or Home Depot. The retail stores build in a big markup to compensate for the ones people steal, so we pay a lot more to cover that. For example, a bolt you might pay $1.00 for at Ace Hardware would be something like 20 cents at a fastener supply place.
When it comes to stuff like stainless steel fasteners, places like Totally Stainless are good sources. Still not cheap, but lots less than buying them one at a time locally.
Don