It probably isn't quite that expensive since you don't buy the floor space with cash but a low-interest, high-leverage loan. And the resale value of that space

It probably isn't quite that expensive since you don't buy the floor space with cash but a low-interest, high-leverage loan. And the resale value of that space is probably over 100%. A better calculation would be annual costs. So say 2% mortgage × €5000 = €100/year. While the treadmill is €1000 / 5 years = €200 / year.