I was recently building a web portal that could accept payments. I was looking into ways to avoid the extra credit card fees we'd have to pay to accept them. I was told I can't charge an additional "credit card fee" because a lot of states outlawed them, but was told I could just relabel that fee as a "convenience fee" and it would be completely legal.

The hotels receipts I've seen (I worked approving travel expenses, so I've seen a lot) they differentiate between specific locally mandated fees and their own fees (which is probably part of the legislation that compels them).

They do that with shipping items on ebay all the time. cheap item price 100+ shipping

That's like renting a flat and being charged extra for doors.

So literally no itemization, just $520.

OK, that is indeed bullshit.

volatile, unpredictable or fluctuating operating costs and fees

Socialize the Costs and Privatize the Profits

edit: What confuses me is how these things can be "volatile" and "fluctuating" before you bought the ticket?

If it’s an airline, it’s likely to allow them to more accurately predict passenger weight. Planes have weight ratings, and need to be sure their loads are distributed appropriately, (like not having everyone in the very back of the plane). Differentiating the tickets will help them flag potential weight problems before boarding even begins.