This week's cover story, Cheat Local!, explores how local businesses get crushed buy daily deals sites like Groupon. As the article explains:

"There is no upfront cost to the business running the promotion. Groupon typically keeps half of the discounted price, and reimburses half—so, $5 of the original $20 price of [an item]—to the merchant."
We put together a tool to help you work out just how much a local business will make from that daily deal that just landed in your inbox.
Price of product/service $
Percentage discount %
Percent taken by deals site %
Amount kept by retailer