I mean, I'm not sure about the server costs, but I don't think they're that large. Maybe I'm wrong, but Bethesda already has ESO servers and has probably either figured out how to use those for Fallout 76 or get really cheap server setups.

It's probably the refunds and whatever they have to do to keep from being sued over the "canvas" bag that will lead to any issues.

I don't know that Fallout 76 is going to necessarily suffer an early death, but it's basically Bethesda's Fallout Tactics.