The problem with increasing the price to a ridiculous amount is that buyers will see that and assume that the seller is a shonk and a charlatan and will decide to report the listings/seller to ebay.

Buyers who make assumptions and jump to conclusions can cause havoc when there is no justification for it at all.

I have seen DVD sellers increase the price of a single set to $999.99....obviously they are out of stock.  If the seller had done it with every listing I would be rather suspicious of their motives.