Sounds to me like HTC's margin is pretty slim and Steam's cut would be more than that margin.
But if steam takes 30% from sales, so that leaves 70% to developers, are the server running costs higher than what would be from the 70% ? Does steam want more from HTC than 30% ? If yes, then it is understandable, but otherwise the profit should always be +x.xx %
AFAIK there is only one time fee of 90$ to put a game on steam greenlight,
btw steam is removing greenlight in spring and doing something new
'A better path for digital distribution
The next step in these improvements is to establish a new direct sign-up system for developers to put their games on Steam. This new path, which we’re calling “Steam Direct,” is targeted for Spring 2017 and will replace Steam Greenlight. We will ask new developers to complete a set of digital paperwork, personal or company verification, and tax documents similar to the process of applying for a bank account. Once set up, developers will pay a recoupable application fee for each new title they wish to distribute, which is intended to decrease the noise in the submission pipeline.
While we have invested heavily in our content pipeline and personalized store, we’re still debating the publishing fee for Steam Direct. We talked to several developers and studios about an appropriate fee, and they gave us a range of responses from as low as $100 to as high as $5,000. There are pros and cons at either end of the spectrum, so we’d like to gather more feedback before settling on a number.'