Never mistake ignorance for stupidity. Ignorance is curable.
...so if the buyer didn't know he probably could have obtained the coupon free from another source, did he get a bad deal? He still got what he paid for, and got the tool cart at a discount from the normal price.
Count me in the ignorant camp until recently. I now know it's usually easy to find the coupons online for free, and that HF sometimes doesn't follow its own policies -- allowing multiple discounts, for instance. All ya gotta do is ask in a nice, friendly way.
Now, if the seller was using an alias (or a confederate) to bid up his own auction, there's a term for that: shill bidding, and it's against eBay's rules. Oh, yeah, there's another term: fraud.