Joshua Tallent is a "professional eBook developer" and he charges $40 per hour (1/2 hour increments) for Kindle and Mobipocket eBook conversions, see
Kindle Formatting Services. Joshua is probably getting top dollar because his conversions are very good. See
Extra Large Print Kindle ebooks and
Rand McNally Road Atlas on the Kindle. There may be more of a market for Kindle conversions from individual authors than for eReader conversions. Does eReader (or FictionWise) even have an author contributed sales mechanism? On the other hand, the two examples above are for conversions done for publishers.
You may want to offer iPhone optimization as part of your eReader conversion, since this is now a major selling point for eReader.