Earlier quoted context omitted.
They're not unprofitable in general. They are for Fidelity, which is using it as a loss leader to keep their customer base from fleeing (Fidelity has a lot of overhead as a financial services firm).
How do you know? Unless you have some actual evidence you're just making things up. Fidelity's largest fund is an index fund[1]. Do they make less money with index funds vs actively managed funds? Probably. I see no evidence that they are losing money on them and ample evidence they are profitable. [1] https://www.bloomberg.com/news/articles/2016-12-02/fidelity-...
> If Vanguard's index funds are run at-cost, then how does Fidelity make by undercutting Vanguard's rates?
https://www.reddit.com/r/investing/comments/62fbk9/if_vangua...
https://www.fidelity.com/mutual-funds/investing-ideas/index-...
http://www.ft.com/cms/s/0/6663cd8c-410d-11e6-9b66-0712b3873a...