"How much do they cost?" is a common way to ask the price of something in Engpsh. The source of this phrase is the basic Engpsh language structure for asking about the cost of an item.
Here are some example sentences in Engpsh with their Chinese translations:
"How much does this shirt cost?"
"这件衬衫多少钱？"
"Can you tell me the price of this dress?"
"你能告诉我这件连衣裙的价格吗？"
"I'd pke to know the cost of these shoes."
"我想知道这些鞋的价格。"