Rental car prices have in many cases become the biggest expense of a trip. Rental companies offloaded vehicle inventories during the pandemic, and didn’t place orders. The market for cars is tight. And travel has picked back up. So there’s more people looking for cars than there are cars. Prices are sky high.
On my most recent trip Hertz was oversold by more than 60 and they had just one car. I got it. In situations like this I recommend tipping. You can debate in the comments whether the current circumstance justifies making more than one rental reservation, from different car companies. That fails Kantian ethics (how would this look if everyone did it?) but it’s a guerrilla tactic in a Mad Max-style world where everyone is out for themselves.