Islam gets around this the same way they get around no sex before marriage. With a bullshit workaround that god is totally cool with because it follows the letter but not the spirit. You can marry someone for an hour and then divorce them. Totally halal prostitution.

A loan with interest these days for 1 million USD at 6% interest over 20 years will have you end up paying 2.5Million for that 1 Million house. It’s bullshit but it is a system that somewhat works. If interest goes up you pay more, interest go down you pay less unless you have locked in at a fixed rent.

In Islam the banks still want to make money of course so they just pre calculate this and call it a fee. It ends up being interest, baked in at a fixed price.