I'm wondering if its related to underestimating support costs, freeloaders in the Nano tier, or if it's an experiment in pricing elasticity.
Note: old prices (emphasized), via Google's cache, added to original email below.
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Dear Redistogo User,
We're contacting you to inform you of a price increase for the Redistogo add-on. Effective today, the new monthly pricing will be as follows:
Nano - free
Mini - $9 (up from $5)
Small - $39 (up from $25)
Medium - $169 (up from $110)
Large - $390 (up from $300)
Super - $1200 (up from $1000)
More details on features can be found at http://addons.heroku.com/redistogo.
As an existing user your current pricing will remain for 30 days. On August 24, 2012 your service plan will switch to the new pricing.
Best,
The Heroku Add-ons Team