Don't want to fork out for a complete module/handbook/campaign for someone else (e.g. your DM)? Currently getting paid to run campaigns, but then need to give paypal a cut before buying more content for your players? Why not just have the ability to buy credit in the marketplace? Just have credit as a $1 item in the marketplace, maybe the option for recurring payments, like the subscriptions. Then DMs can redeem for content, to the benefit of themselves, their players, and Roll20...