I'm guilty of messaging sellers and asking them for a better price, sometimes they don't reply, sometimes they say no, and sometimes they come back a few days later asking if I'm still interested in that price.
"if you don't ask you don't get"
regarding the Auction vs BIN, this is pretty tricky, when I started ebay I would list 90% of my items as auction but now it's the opposite, I usually only have a very small margin of profit with ebay fees, paypal fee's, taxes, time spent. When auctions turn out bad and you get way lower than you expected it's sole destroying lol
Lately I've been listing items as BIN over 30 days for the highest price possible, and then lowering it every 10 days or so, I don't mind waiting for a bigger price. Plus if you have an ebay shop you can run sales too which I need to do more of.