Found some for $3.18 a foot, that's crazy expensive, but I agree that for going that length where line loss would become noticeable, it'd be better to get the best you can afford and not worry about it ever again. I might just help him do say 100 feet of RG8U for now, and then save up the money to get something better later. Seems like all of really low loss cables out there cost a pretty penny.