Well, sometimes they go for too much just because it's a clone or Jedi, then I see someone make a custom that really has a lot of work go into it that doesn't go for too much, which leaves me scratching my head.
As for the seller that apparently was rude to you starkid, just brush it off your shoulder, don't worry about it. We'll offer you advice here anytime. Besides, he doesn't post here in the customizing section from what I've seen, but has made some nice customs. He might be a really nice guy, but I don't know why someone would ever act that way when someone asks for help, but I've seen a customizer at Scum do that before. He used to post his work, then when people would ask how he did it, he wouldn't tell because he said that would take away from what he could get on ebay. That was pretty sad. I haven't seen him post in a long time there now though.
I've sold a few customs on ebay before, but usually had them for sale here first and always offer advice if someone has a question. Sometimes it's just easier to go on ebay to sell a few things rather than in a classifieds section because it's hard to keep up with 5-10 different people sending you PM's back and forth. So I don't have a problem with people selling their customs or their collections on ebay at all. When they buy up new figures at retail to try and make a buck on ebay though, that's where I get disgusted. Like seeing so many new SAGA2 Sandtroopers on there makes me sick.