i don't like making offers. i like to put the onus on the dealer, asking what's his bottom dollar then give him credit for enough integrity to be honest. at that point, i either buy it or don't. if i decline and he says "make an offer", sometimes i will.
i've known enough dealers who said they hated someone asking their best price, giving it, then the alleged buyer low balling it. "i just told you my best price and you're offering less?" that's the main reason i like dealing with the same people. dealers who know me tell me their bottom line and i give them credit for the integrity to be honest about it. makes life easy.
regarding the other matter, i one time and one time only asked a dealer if he'd take suchandsuch for something. i was only half interested and had no idea he'd take it. he slapped a 4473 on the counter and i said "well, i guess i just bought that one didn't i!" learned that lesson cheaply at least.
conversely, one time i was set up at a show and a guy asked "will you take suchandsuch for that?" "yeah; i'll take that." "OK. i'll think about it." i went from zero to pi$$ed off that quick. "think about it? listen, feller! you made me an offer and i accepted. you just bought this!" he walked off and for the rest of the show never came back by my table. he'd get part way down the aisle and turn back instead of coming past. unfortunately that's extremely common.
it comes down to a person standing behind his word - both buyer and seller. after getting behind the tables at shows when i lived back east, i learned why some dealers seemed such jerks. years or decades of putting up with buyers. found out when i was wearing an exhibitor badge most were the nicest people you'd care to meet.
roger