Common sense says you can't force anyone to sell if the price isn't what they want for it... And you shouldn't try to, it makes you a douchebag.
You are ****ing kidding, right?
A deal is a deal.
I have expended thousands of words here exploring every aspect of ebay, more of it negative than positive, and much of it revolving around the fact that sellers need to be careful and mindful of exactly what they are doing, and the consequences, all the time.
A seller who reneges on a legitimate sale is a ****ing *******, just as a buyer who reneges on a legitimate sale is an equally large *******.
If you don't want to sell your item for less than $20 but start it at $0.99, then you are an idiot.