In Texas who is liable to pay with an infested apartment with bedbugs? If the tenant is responsible for bringing in the bedbugs, how is it legal that the apartment complex has to pay the price for there decisions.

Who says that the apt complex has to pay the price?

I run hundreds of apartments myself and have also suffered from pest (including bedbug) issues, so what I've done is add an addendum to the lease (that the tenants have to sign before moving in) that affirms that the apartment is pest free and that bedbugs, fleas or cockroaches that become known of after the tenant moves in are the tenant's responsibility to remove.

I handle the extermination and charge the tenant - when issues like this come up.