I spent 3 hours and $20 worth of gas a while back trying to find a couple of 1/2x3-1/2 Stainless Steel bolts in decent quality. By decent I was willing to settle for 18-8 grade. The only stores in town that had ANY stainless in that size was Ace Hardware. I asked what grade they sold and they said they didn't know so I drove to the store and went to the bin with a magnet. Sure enough every SS bolt in the bin was magnetic. Not what I'm going to stick in the transom of a boat that will see salt water.
My want had nothing to do with cost. I simply wanted a good quality part. The size was even a compromise since I really wanted a 3-1/4" length. I tried calling a few places and got no help. One girl at a auto parts store told me to come look in the bin for myself. Two places said they had what I wanted and when I got there neither did. I was able to check stock for a few places that would have been open on Monday and neither had it in stock according to their web sites.
I ended up coming home and ordering 316 grade in the exact size I wanted from McMaster Carr. Their packaging for matching nuts and washers were 10 per pack so I went ahead and got 10 bolts just in case I needed them in the future. I spent $48 for my task that needed 2 bolts, 4 washers, and 2 lock nuts. Had it in 3 days instead of their usual next day.