Bloons TD 5

Note: This trophy seems to pop with a delay. After upgrading all buildings to the maximum I started a new game (monkey lane on Easy) and just played till it popped, which was within the first five waves.

In the Specialities menu, there is a Speciality Building for each tower which can be upgraded four times. This will cost you a total of 74,550 in game dollars (green). A Speciality Building, improves the tower it is for but devalues another. You may also have only one active at a time. If you play mostly with FastTrack and Double Cash I'd recommend to use the Super Monkey lair most of the time since it will make Super Monkeys see Camos and that basically means you don't need anything but Super Monkeys for most of the game.

If you don't want to waste money on Speciality Buildings, then do the following:

1: Backup your save once you have enough cash to buy all the Speciality Buildings at once.
2: Buy all of them at once, then quit the game and return to the XMB.
3: Restore your save from where ever it was you backed it up to, then reload the game.