In 1970 there were essentially two methods of protecting steel beams from a fire; encasing the steel beam in concrete or the newer, more cost-effective method, asbestos.
When asbestos was banned in 1970, and concrete encased steel beams were not an option, as the WTC were at around the 67th floor; "suddenly" a new method to insulate the steel beams was invented.
Yes the WTC most likely would have eventually imploded, but I believe the towers would have stayed up longer had asbestos been used.
That's not the same as being "built on the cheap", which was what you claimed. The builders had fully intended to use asbestos all the way up, and were prevented.
What proof do you have that the alternative fireproofing was "cheaper" than the asbestos they had planned to use in the first place? If it was a "new" process it could very well have been more expensive. Where's your comparative cost analysis for both materials in 1970? Let's see it.
In any case, the fireproofing would have been perfectably adequate for a FIRE. The problem, if you saw the show last night, was that the impact and subsequent explosion blasted the fireproofing right off the steel in the impact zone, so its effectiveness was a moot point. And the other fire-suppression methods failed as well. Everything that could have gone wrong did go wrong. It wasn't just the coating on the steel.