'buy cost' is not correct and usable in written English.
In written English, you would use 'cost of purchasing' in a sentence such as: "The cost of purchasing a new car is expensive."
Everything we buy, costs have increased.
But more than two-thirds of what consumers buy costs less than $10 per bottle not the stuff the critics spend too much effort concerning themselves with.
The first three posts he bought cost two bottles of local gin.
The power it bought cost less than the price of constructing a plant.
The apartment they end up buying "cost a fraction of the same apartment in town".
After a couple of Medalla beers (prices varied, but the three-can round I bought cost $5.60), Nacho took me to a bigger, crazier scene — La Placita.
The ones I bought cost £14 each, so it could prove an expensive disappointment, but the savings in the long run can be considerable.
Buying cost of components from collection centers includes buying and transportation costs.
Today, two-thirds of machines people are buying cost less than $1,500.
