Here's the problem with generically asking "what should I buy?" -- every experienced collector is going to immediately mark you as just another speculator trying to make a quick buck. And yes, that will elicit a lot of snide responses because that isn't what the majority of us are here for, nor are we going to do market research for you. Now, a question like "what are some good Spider-Man/X-Men/Wolverine stories that I should be on the lookout for this weekend?" will definitely get you places.
Why would anyone label you a "thief" for putting a premium on your books on a site like eBay? People do it all the time.
You're really going over the top on this. Just because dude was asking $250 on X-Force 11 doesn't mean he's trying to defraud someone. Its a comic book, not a bundle of junk mortgage backed securities falsely rated as AAA. What you see is what you get, and what you pay is what you think its worth. If an inexperienced speculator shows up and pays sticker price, lesson learned for Mr. Speculator.
But odds are also good he's never going to sell it at that price based on the current market. If he's too inflexible in his ways and shuns negotiation, then the market is going to punish him in the end when he's stuck with a bunch of overpriced inventory.