It's all about quality and selection!  To purchase stainless steel nuts locally I would have had to pick up many, many of the little plastic bags that have three or four nuts.  At Amazon I was able to purchase these by the box, at a really great savings.  These are really fine nuts and having them available in stainless steel is a real bonus.  Once you start using stainless steel you will never want to put up with plain old rusty steel nuts.