Thay are at a good price.这里为什么用的是at?

Thay are at a good price.这里为什么用的是at? She wants to buy shirts at a good price.请问这里的介词为什么用at?可以用 wi at a very good price为什么用at 价格合理是at a good price还是at good price at a good price 求英语翻译,急我们有许多价格合理的东西.We have things at a good price.这里的price要 we have sweater at a very good price为什么用at? They are at a very good price.(改为同义句) The clothes at MrCool's store are () a good price. Are you good at dangcing?这里的为什么要用Are? They _____ at good price.用have还是are at a good price 还是 for a good price