While you can find a decent price per foot on SPT cable from many online vendors, it all falls apart once you add in the cost for shipping. Copper is very heavy.
If you buy it as part of a large order and they throw in free shipping, it would be worth it. Otherwise, you can't beat Home Depot $42 for 250' roll of SPT1...and its always there if you need an extra roll at the last minute.
Mike E.