TL;DR; Software pricing is complicated, the answer to your question is all of the above.
While Magento Community edition and Magento Enterprise Edition are very similar, there are differences in the two platforms. Does the extension work with EE's full page caching? I ran into an EE bug with Commerce Bug (the Magento debugging extension my business sells) where it wouldn't work with a version of EE's private sales feature. Beyond these specific examples, an extension business needs to look at the fact there are differences, and those differences will incur either additional development time, or additional support time.
It also means an extension business that's providing EE support needs to have access to a copy of Enterprise Edition. If an extension developer is on the up and up that means a partnership of some sort with Magento Inc. which is a cost — both in fees and in maintaing that relationship.
Finally, what you call profiteering another business might call price differentiation. The murky truth is somewhere in-between.
As a very small business owner selling extensions, I've thought about charging more for Enterprise Edition support — but at the end of the day my support workload didn't have a lot of Enterprise Edition related questions, and a significant portion of my customer base are developers who actually like working with me to solve the problems encountered. Even for customers who aren't developers, the fact I'm willing to jump into their system to solve EE specific bugs (or CE bugs for that matter) leaves them feeling good about their purchase and they're more likely to buy from me in the future. It even occasionally leads to a small consulting gig.
That said, I can easily see how a larger scale extension developer selling to a less technical audience would need to raise EE prices to help keep their business afloat and growing. Like I said, software pricing (and business in general) is complicated.