What is the ruling on increasing the price of spare parts on the invoice for workshop owners, knowing that workshop owners refuse to buy parts at the original price and prefer to deal with those who increase the price for them?

What the owners of these shops do is devour people's money unjustly, based on the Almighty's saying: ﴿O you who have believed, do not consume one another's properties unjustly,﴾, and based on the Prophet's (PBUH) saying: "No flesh that has grown from unlawful earnings will enter Paradise; the Fire is more deserving of it." The shop owner and the workshop owner share in the sin, and Allah Almighty removes the blessing from such money. Through piety, Allah will bless your money, even if it is little.