I buy from Midway with some regularity. I have always had good service. The shipping costs were much worse before they instituted the new shipping program(although not as good as they were a decade or so ago when they paid the freight). I will say that I seldom buy things that are not on sale, unless it is something I need and can't find locally. I do a lot of my shopping on Friday, when they have the new clearance stuff. Mostly I buy reloading stuff ( Dies and molds), parts and on occasion, ammo or, very seldom, bullets that are on sale, and I do watch the shipping charges and if they are higher than I think they ought to be, I edit my cart and order that stuff later(or not at all)
Now I have to agree with the original poster and all that have followed. A defective part should be taken care of, without additional cost to me. Fixing problems is part of doing business.
Lastly, as someone who has spent more than a little time ordering stuff and things for customers and listening to my accounting department whine about how much money we were losing on shipping and knowing how much we were charging for freight(over and above what it really cost). The cost of fixing FUBARs (like the defective mag, above) is why sometimes the original shipping cost seems high. Fixing things has to be figured into the overall shipping cost program.
I really don't see a lot of difference in any of the places I buy from. I try to shop for deals on the things I need. Sometimes I have to pay more to get stuff I want but I try not to buy from people that, I feel, don't treat me right.