buying individual bolts at a hardware store can get painfully expensive, so often "by the pound" alternatives may be better - but not always. they tend to price somewhere between the individual and bulk prices.
if you're a frequent do-it-yourselfer, then it never hurts to have a few extras on hand. i buy grade 5's to keep on hand at mardens (local used/surplus store chain) - probably have 50+ lbs of 1/4-1/2 bolts, locknuts, and washers at all times. when i want grade 8, i find that even smaller bolts can often be $1 and up EACH if bought individually. find a hardware store with a large assortment, and often behind the drawers of individual bolts, they will have full boxes of 100, or 50, or whatever. check prices on these. often a bolt that is $0.75 individually can be bought in a box of 100 for under $20. if you need 10-20 of these, it's a no brainer to get the box. otherwise, try places like fastenal, or whatever you have locally. their prices for full box are very competitive.
