You can bypass the Steam fee as the publisher. Steam's rule is that you can't sell a Steam key for your game somewhere else consistently cheaper than it's sold on Steam. You're free to go wild with pricing, so long as it's on a completely separate distribution platform.

See: https://partner.steamgames.com/doc/features/keys

(At the very least, if they're trying to do a most-favored-nation rule, they're not listing it in their policies and are enforcing it through back-channels.)