[leoedin]

Surely a fairly core issue is the type of customer who buys from Groupon.

If Groupon deals are primarily purchased by a fairly small core of regulars (in my very limited experience a few people I know use groupon a lot, most never do), then increasing the price one day might just put them off buying tomorrows item. Every person has a finite amount of disposable income.

[nicw]

Exactly. There are so many other factors regarding pricing: Long Term Value, and Cost to Acquire being one of them. It is common to break your audience into 'bands', and learn the trigger points for each band: cost to acquire a customer in this segment and how likely they are to make repeat purchases, at which price.

Simply put, the majority of your audience may make repeat purchases, but only if each purchase is a separate price. This is much greater value than a one-off purchase.