I don't disagree that there is an element of 'I won't be outbid' on eBay auctions.. but that doesn't turn a $3000 truck into a $7500 truck.
For the most part, and with limited exception, people buying on eBay aren't there to pay top dollar for anything.
The exception would be in instances where people are shopping for items that are rare, hard to find, or only occasionally pop up on eBay and are difficult if not impossible to source locally.
A 57 1/2 ton pickup is not such an item.