I don't think 100ft. of cable is too expensive. I might be cheaper than you think. 
Newegg.com - Accessories, Cables, Computer Cables, Network Cables, Network Ethernet Cables, 100 ft..
Alternatively, you could just get a box of 500ft and get a crimping tool and some ends and make it as long as you need. 
__________________
ASUS P7P55D-E | Intel I5-760 @ 2.8GHz | Corsair XMS3 8Gb @ 1333MHz | WD Caviar Black 1TB | HIS Radeon 6850 | Corsair 750TX 750W | ASUS 24x DVD Burner | Antec Nine Hundred | ASUS VW246H 24" | Windows 7 Home Premium 64-bit
|