If the block reward was forever 50, it would have radically changed the long-term calculations of all the early miners.

For example, I probably wouldn't have stopped mining and started buying instead, in August of last year.  I would almost certainly have taken a hard look at what would have been a serious first-mover advantage, and bought more hashing power.

As it is, with the block reward constantly dropping every four years or so, that first-mover advantage goes away.  Equipment costs go up.*  Different people who calculate things differently get involved.

The fact is - as I see it - the whining about 'early adopters' (no different than early miners, really) is probably less today than it would be if the block reward was immutable.

*n.b.:  I'm reasonably certain that sooner or later equipment and electrical costs will become a very tiny part of the mining calculation.  Probably sooner.  Technology marches on, and as Bitcoin gains market share smarter and better equipment designers will enter the fray.  I expect massive - and I mean massive - hashing power to be available within the next two or three years, for the cost of a decent desktop computer.

In the mid-term, I'm convinced that the most expensive part of mining will be space/property costs.