Why did they let them know when there were 5 second left?
 

They should have taken the money away the second after it reached 50,000.

BB should've kept quiet, the counting triggered their reaction, also I didn't like the way the money started to build up, it should've been BB telling the main rules but also letting them know that the money build up was unknown and at any time their chance would be destroyed, then in the proper bidding game a certain amount of money would be named by BB let's say starting with 1,000 wait 5 seconds in silence and keep going up, if the amount would've reached 50k (it would have never reached that amount of money anyway) and after 5 mute seconds they wouldn't have pressed the buzzers then their chance would be gone for good.

This is exactly the way it should've been done