There are a ton of fees added on to rental cars, especially when you rent at the airport, in addition to taxes. I wouldn't have said 2x the base rate but you can definitely hit 30-40% uplift. When comparison shopping rental car pricing, you absolutely have to know if it's the base rate or the all-in price.

Hotels have some of this but the overall uplift is usually a lot less--at least until they start adding "resort fees" to otherwise discounted rooms.