The maths behind this is similar to UK leasehold. With a leasehold (which is a truly terrible system) you pay as if you're buying the flat, but actually you only have a lease usually with a very small annual payment and some management charges. The catch is the lease only lasts usually 99 years and for various legal reasons you have to renew it before it drops below 80 years, and that costs a bunch of money.

Leaseholders are called "homeowners" but they don't really own the home in the normal sense and are closer to long term renters in their rights.