Mad Games Tycoon (UP)

You can increase your customer base by including extra languages, specifying the correct target audience, building hype with your marketing team or showing games in development at the Mad Games Convention, and of course with your games review score. Once you start self publishing your games, you'll have more control to build a larger fanbase through pricing and including the various goodies when publishing a game and printing colour manuals.

At $19 you have access to the entire market.
For every $ below that price your customer base increases by 10%.
For every $ between $20 and $29, you will decrease your customer base by 5%.
For every $ between $30 and $49 you decrease your customer base by a further 1%.

Summary:
$9 - $19: 200% - 100%
$20 - $29: 90% - 40%
$30 - $49: 39%- 20%

Of course, make sure you only try this with a game that's actually highly rated (98% or above). I made a guide for the 100% achievement which should give all the information you need.