Don't charge - release it as Free/Open software.
Then provide way for people to donate whatever they like, based on how useful it is to them. (Unfortunately, I don't actually know how effective this is.)
If this is a core product for your company, you can still do the above, but also a commercial license and support contract, and maybe sponsored feature development too.
(This model is used at big software companies such as JBoss, MySQL, but smaller companies such as BlueRiver or Railo Technologies also do this successfully.)