eBay is weird. I make most of living buying and selling stuff and I often price things with decent prices as I generally find it cheap enough to pass along for a good price and good profit for me as well. Yet, sometimes things just sit there or I'll see same items sell at higher prices than the stuff I have listed.
If I get a lowball offer through the messaging system, I just ignore it and put them on my blocked bidder list. No need to get worked up over it, for me at least.