The thing I like most about McMasterCarr is, I get everything I order in just one day, without fail. Plus where else can you choose a specific thickness of washer? Great for hard to find items.
So I'm starting a minor project and needed some hardware. Specifically 3/8" bolts 4" long McMaster car has them here http://www.mcmaster.com/#standard-cap-screws/=mx2eka
Cost is $14.81 for a pack of 25
So $.59 per bolt
the trick is knowing what your hardware store carries and planning ahead. There's something to be said to "have it right now" and McMaster cannot offer that. If i need a bunch of two inch 1/4 20 bolts right now, i'd go to the hardware store. But if it's 1/4" 8 32 pan head machine bolts, I know local hardware store only goes down to 3/8", it would save you plenty of gas money driving all around town.