Allow BYOK models without key, now that usage is based on model price

Now that usage scales with model cost, could more expensive, currently key-locked models be allowed for everyone? They could have proportionally higher usage impact to account for their higher costs, while giving everyone the chance to use them.

Could be combined with allowing keys for all models, as others have suggested, to give people the option to use all models within reason, or bring their own keys for more.