My fiend you are in a tough spot. I know the feeling (not with a gun however), your dammed if you do and dammed if you don’t. As far as the cartridge goes, if don’t have one and you think that you may use it get the gun. However as for the price, you are looking at the steel of the century. Now what to do? It sound link you friend must really value and respect you to offer such a “gift” IMHO buy the gun and if you can don’t feel right about the price, and can give him more then do so. It seems that from what you say he does want you to have and use the rifle. Just my .02’s