Chopper are unaviable to buy

Good day!
There are few things that are unable to buy.
For example helicopter KA, it costs 300 000 gold, that's 300 briefcases.. And where is the problem? There is no possible way to have 300 briefcases in one moment in your inventory. That's make this helicopter unable to buy. Same with few planes.
I don't want from you to decrease the prices rapidly. Just decrease it so it is possible to buy that stuff.
Thank you and have a nice day!
JaesonCZ

Some vehicles are for missions purposes only. There are missions where you need to steel vehicle e.g. KA-52 which you can sell at traders then.

Ok I get it. So there is the mission where you can get SU jet?

yes