How to increase construction number capacity before it’s reached to its cap?

Construction vehicles can be built with resources up to 2 times I think, but after that it does start costing a little money. I have 7 construction vehicles but to be able to get the final 8th I would need to purchase a 50$ pack which that won't happen any time soon. the first pack to get a construction vehicle building I think was 4$ then got progressively more expensive after that.

it has been awhile so it could be 3 or 4 before it starts costing money.