Hey Guys

I am doing a project for one of my college classes on Boeing Aircraft Company and was trying to find out how much they sell for, for example when an airline buys them direct from the company brand new? I was trying to find the values of the 737, 747, 767, 777, and the BBJ. I have looked on websites but they all say please inquire or make offer. Plus they are all older planes. Any help would be greatly appreciated.
Thanks

RSD