For me, the rise of preprints has blunted the impact of that exclusivity period: something approximating the full text is usually available, whether from the publishers, PMC, or bioarxiv. This might depend on a lot of discipline--neuro dove head-first into preprints and I think they're less common in other fields.

It's not obvious to me what the "right" fee is. The NPG fees seem bonkers. The PLoS journals and eLife aren't trying to turn a profit, are a bit lower but still in the few thousand dollar range, so there must be some non-obvious, non-trivial expenses.