That's effort not expense, regardless don't you think that Satoshi Nakamoto put in the same, if not more, effort and didn't pre-mine BTC.

I'm not sure why I would compare the two.

If OpenOffice team gives out their software for free, does it mean that Microsoft is somehow morally evil for selling their own Office package?

Difference between effort/expense does not seem to be important here, the point is that Ethereum developers put something real into it (work, resources, etc - quantifiable and provable), for which they claim that they should be reimbursed in form of a pre-mine. This information is publicly available, and known by most network participants, who still voluntarily participate in it. I don't see any problem here.