I don't know what Prolific is currently paying, but even at that rate an increase in filesize could easily be prohibitive. Traditionally we've sold roughly 1 copy per 1000 downloads, which (just a rough guess here) probably works out to just under a dollar's worth of bandwidth per sale. A dollar is a fairly large amount for Prolific to absorb, and if the filesize were to double, they'd have to lay off poor Josh!
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