hmm so assuming 30 work well that would be around $20 each. if the 3g is not provided you can complain to the seller/ebay/paypal? that the product was falsely advertised. While the seller does say no refunds, false advertising might be able to get you your money back.
Good luck with the Kindle Dxs
its ok to lose an auction if you feel the prices for each good kindle is too high. I'd guesstimate the number of working kindles you expect to receive from the auction and what reasonable price you expect from each.