Abebooks is my primary source of buying books! Its especially good for me, since I'm not originally from the US and its the cheapest way to get publications in my native language from "foreign" sellers. I'd like to support booksellers in my country, but I go back only once or twice a year and can't make all purchases then. On the other hand, I've found sellers that are shipping from within my city or around (happened thrice in 4ish years of buying). In that case, I'll just track them down and try to contact them for a direct purchase cutting out the middleman. Its a lot of work sometimes, but in my mind worth it.