On half price heli costs go as such
225k - Hummingbird
500k - Orca <----- Green can be scrapped by players
2 Mil - Hellcat
3 Mil - Mohawk
15 Mil - Huron
25 Mil - Blackfish infantary <-------- Ones in red can't be scrapped by players
Full price means all of those prices are doubled. They're expensive because being able to fly around the map doing runs is extremly powerful. Don't like the look of a situation? Fly away. The prices help to keep the server balanced.