In the Apple store, if you got that many downloads and that kind of placement, the traffic from the various lists and high placement for 7 days would convert to many many paid sales over the following days.
Section 2.a. of the Amazon Appstore agreement, emphasis mine:
"a. Royalty. For each sale of an App, we will pay you a royalty (“Royalty”) equal to the greater of (i) 70% of the purchase price or (ii) 20% of the List Price (defined in and subject to section 5i) as of the purchase date. No Royalty is payable for Apps with a List Price of $0.00. Such purchase price excludes taxes and any separately stated fees or charges. A Royalty is due only for sales for which we have received final payment from or on behalf of an end user. If an App is purchased using a credit card or bank account deduction mechanism, final payment will be deemed to have occurred when the applicable credit card company or bank has fully settled the payment for the applicable purchase."