Your math is wrong. The 12% you are saying is curation + hive apr.
Hive apr now is around 3%, and it goes to the owner of the HP and not the lessee. The lessee get only the curation rewards that rarely reaches 9%, if you are a very good curator you will be between 8%-9%.

The apr shown in the lease price also does not count the HP cool down period for returning the lease. So if you are leasing for only 4 weeks you are actually paying around 11%, not 9.74%.