The reason there are so many responses to WTB threads that comment on "not offering enough" or the like is because they come from people who aren't doing the content (in this case, Ou) frequently enough to understand what they are asking for.
You might value the drop itself at 20mil, and that's fine. You're more than welcome to seek someone selling them for that, and if you succeed, bravo. But when you're asking a group to give up a minimum of 6 runs (5 to build the popset, and then a stupid lucky 1/1 on Ou for the drop you want) to go after a drop you want, you're not just paying for the drop.
Several groups are done with Ou, and are literally doing nothing but 8 Keis a week for Shamash Robes (or fill in any of the lesser bosses) because that's all their members need/want from Omen any more. Your request to go after an Ou drop to that kind of group is actually a hassle.
Don't take these posts of "too cheap" as an insult. If the responder in question actually didn't give a ***whether you got your desired item, they wouldn't post at all. It's actually solid advice to try and reach more potential sellers.