I suspect this permissiveness was a major reason it was never hacked throughout its full 8 year lifespan - homebrewers didn't need to enable piracy to do what they wanted.
- xbox always charges you for the privilege while apple has a free developer tier. The free tier is limited (no distribution of apps you wrote, app will time out and have to be reinstalled).
- xbox requires you to put the console in developer mode, which eliminates your ability to play commercial games. Apple does not have this feature (although some commercial apps do attempt to detect things like jailbreaks themselves).
So while the xbox developer mode might give homebrewers more capabilities than a developer account by apple, it doesn't affect revenue sharing for companies who want to make a profit off of their work.
Edit: can't reply further, but this can indeed be done for free (assuming you have access to a mac or a mac vm). The paid developer account is only for publishing to the app store, you can do almost everything with a free developer account.