The shipping is high, but there are usually several factors as to why people do this.
First, the cost of shipping an item between a state, ie, could be $10 via UPS. If he was shipping from FL to WA, it may cost $15.
This may not apply to retailers, but it does cost money for boxes, tape, etc.
Lastly, ebay takes a cut from everything but shipping, and they do advertise what their shipping cost is, it's not hidden somewhere in small print.
Anything other mislistings is wrong, but if you see everything right in front of you, caveat emptor. Ever see those infomercials? Buy one get the second free, just pay shipping, yet they don't tell you shipping is like $20 for a mop.