If someone moves into a $4K apartment, it doesn't make the $2K apartment more affordable. It only makes it available which means someone living with roommates in a $4K apartment will probably move into the $2K apartment by themselves.

What's also likely to happen is a landlord will see that somebody moved to a higher price department, do a spiff and spit job to fancy up their apartment then charge $3.5 K.

Building more expensive condos will not do anything to drop the cost of an apartment. It only free up lower-priced properties which are still too expensive.