Base prices have generally been going down since the 90s https://www.bts.gov/content/annual-us-domestic-average-itine....

It’s not enough data to attribute the impact of the broad switchover to baggage fees in 2008-2010, as base prices actually went up after introduction, but base prices are definitely down over time.

When there's competition it works. For example in Europe the airlines with the most fees also have by far the lowest base prices.

The problem is if for a specific route or airport there's only one airline. That seems to be somewhat common in the US, and in that case price isn't constrained by competition but the customers willingness to pay. That's where the abusive practises flourish

When you look at Ryanair’s prices, it is often readily apparent that they did.