Hate to respond to pedantry with more pedantry, but that's a pretty questionable application of micro theory.

The main value of using Groupon is that in exchange for offering a deep discount, you get the firehose turned on your business - it's a customer acquisition tool, using equal parts advertising and pricing. Businesses wouldn't get the same demand spurt by offering discounts without using Groupon.

What the author gets right is that it's an open question as to whether merchants can convert the discount buyers into regular customers.