>So air bnb charges more than landlords?

Per day yes. Also you don't need to have a lease or a tenant with rights when it's a bill per day situation.

>Why wouldn't landlords jack up prices as much if they feel they can?

They do.. Also companies exist that employ algorithms to sell to land leeches landlords to calculate rents/air bnbs/estimated mortgage payments in a given area among other factors to help them jack up the prices every chance they get. It's a big fucking problem.