ARM server vendors don't have to win the game, they just need to score points. Intel NEEDS to win... Like you said, it's a market that's too important to cede. But selling server processors at cost is not an option that Intel could sustain for very long.
You do know that the current ARM/Intel debate as far as the server market is concerned is only for microservers, don't you? Microserver market as a percentage of the server market is forecasted to be only in the 5-10% range even by very optimistic IT analysts.
Intel will not cede that wimpy core microserver niche because it will provide an entre to the higher-end market for ARM. By doing this, Intel will make sure it has pretty much the entire high-end server market.
So, no, Intel can sell its microserver offerings at-cost for a long time. Can any ARM vendor do that, I don't think so.