A cheaper alternative may be a track feeder on standard table saw.
My buddy has an older one and it's massive. I'm sure they come up in auctions. I had a large mill saw some 14' Cypress boards on their straight line machine a while back and they were not very straight. I made my own from a RAS with a 28 ft long table and a 20 ft long fence. It worked great. http://www.woodworkingtalk.com/f2/evil-machine-28461/
That sort of commercial machine is not what most of us here use or have access to ...FYI.
My buddy has an older one and it's massive. I'm sure they come up in auctions. I had a large mill saw some 14' Cypress boards on their straight line machine a while back and they were not very straight. I made my own from a RAS with a 28 ft long table and a 20 ft long fence. It worked great. http://www.woodworkingtalk.com/f2/evil-machine-28461/
That sort of commercial machine is not what most of us here use or have access to ...FYI.