Dart Training Facility is the Specialty Building for the Dart Monkey. It costs 500 to initially purchase and increases Boomerang Thrower cost and upgrades by 5%. It costs 1750 to fully upgrade unless, on mobile devices, it will cost 2950.
This can help out in the early rounds, but it becomes almost useless afterward unless the player plans to get Super Monkey Fan Clubs. However, this is extremely useful in extreme tracks, as the player can start with multiple Dart Monkeys, thus allowing the player to get Banana Farms earlier.
Place the free Dart Monkeys wisely because they cannot be sold for any money, however, they can be sold for money if the player upgrades the Dart Monkey.
Dart Monkey upgrades are very cheap anyway so this would be best used for daily challenges that have Dart Monkeys, but no other good towers.
If the player has the Tier 4 Dart Training Facility, then the player wouldn't need to have a Bomb Tower, a Mortar Tower, or an Apprentice to pop Lead Bloons, making this Specialty Building extremely useful.
However, when upgraded to Triple Darts, only the center dart explodes. Furthermore, the Spike-O-Pult is not explosive nor destroys leads.
In BTD5 iOS, despite saying that it will attack 10% faster, it will actually attack 50% faster.
In BTD5 iOS, there is a random mission called "Precision Pineapple," in which where you can only pop lead bloons with Pineapples. However, if you have the Dart Training Facility activated with Level 4, clearing the mission is possible if you have any Dart Monkeys included, making Pineapples useless.
Activating a Dart Training Facility will make 1/3 Dart Monkeys on Medium as cheap as they would be if Dart Monkeys had Monkey Knowledge Packs of Rank 2 Monkey Tycoon and Rank 1 Dart Monkey in Bloons Monkey City, even though combined the upgrade lowering in BMC would only be 2% with a 3% stack. This is because of how low-cost Dart Monkeys are and that every cost amount (includes base costs and upgrade costs) is rounded up or down to the nearest 5. However, 2/3 Dart Monkeys are only $5 more expensive due to Enhanced Eyesight being $5 more expensive.