Why are Magento extension providers charging extra for enterprise versions of their modules?

I have a pretty good idea that the codebase for both of the module versions will be identical so where does this extra cost come from? In some cases i have seend > $100 for the enterprise version.

Why are Magento extension providers charging extra for enterprise versions of their modules?

I have a pretty good idea that the codebase for both of the module versions will be identical so where does this extra cost come from? In some cases i have seend > $100 for the enterprise version.

Is this:

1. An extra cost due to extra technical complexity (i cant see what that would be)
2. An extra cost due to Magento licensing somehow
3. Profiteering since enterprise clients are likely to be able to pay more
4. Something else?