Yes you could, of course you'd have to pay the merchant fees for the transactions, generally around 1.5%. Plus you might have tax issues to deal with(both sales and income). So you'd be spending a lot to get the miles. Of course you might be able to get around the sales tax issues by returning the good to the seller(yourself), then you the buyer would be entitled to a sales tax refund. If you could convince the state and the feds that there was no income involved, see a tax expert, you be down to the merchant fees for credit card processing.

The lowest fees I've seen are 1.48%, which means a 25,000 purchase would cost $370.
On the debit card it would get you 12,500
miles.

Sounds like a losing deal to me.