Controlling station buy and sell prices?

In my universe, there are three hover bike suppliers. First one is in Dymapa, and it is still crawling with Black Sail activity, so most traders avoid that one. Second one belongs to TEF, which went destitute a while ago and cannot buy any materials to produce more hover bikes, therefore it is never able to supply anything. And the third hover bike supplier belongs to me, I have plenty of supply, Galene and Beta Pindola trade stations demand the bikes, yet no one trades with my vehicle factory.

On top of that, no matter how much hover bike stock I build up, my vehicle factory always stays the most expensive option to buy from. Even the TEF one with absolutely no supply appears to be preferred over my factory. I hope getting a trade station of my own will remedy this issue somewhat, but maybe there could be a way to manipulate and reduce the selling price of the hover bikes in my factory, so that traders would prefer to buy from me?