No. You are talking about the nominal value at which they sold , not their actual value, so use "prices"not "costs". Costs" would also mean "expenses".
By the way, quietdandelion, I am getting quite concerned....You are going to outpost all of us here soon. I can't help it--this is my job. In a few years, I could retire. If I don't have to teach, I'm not going to ask so many frivolous minutiae.