When you rent a propane tank from the propane company you'll never own the tank and be paying that tank rental fee for years which can add up to a lot of money over the years.
So when you rent that propane tank you pay the monthly rent on the propane tank which is added to the cost of your propane.
So yes in a way you pay more for propane when renting a propane tank.
If you own the propane tank then you don't pay the rental fee on the propane tank so your propane cost is cheaper.
Although with a rental propane tank the maintaining is done without additional cost by the propane company.
But still owning a propane tank is much better than renting one because it will save you money.
With a rented propane tank you're also only allowed to use the propane company that you rent the tank from to buy propane.
With an owned propane tank you can choose more than one propane company in your area and get the best price on propane.