I was going to order some polyester webbing from the web when it hit me that most tie down straps are made from polyester. This prompted me to head to my local Harbor Freight Tools.
They had a set of 2 x 15' 1 inch wide polyester ratchet straps for 7.99. That's 30' (2x15' peices) of 1" polyester webbing with a 1500 lb breaking strength for .26 per foot. The also had a 12' lockable tie down for 2.99 or .25 per foot. The set also came with 2 x 6' locking tie downs but 6' is not long enough to use for suspension straps but they would probably make a great set of tree huggers. All for 7.99. On sale.
The poly webbing is much more pliable and seems a little lighter than the Speer polypro that I am using now. I will weigh both straps and confirm the weight difference. They also have a higher breaking strength at 1500' lbs as opposed the the 700 lbs for the polypro. Polyester webbing is supposed to be more abrasion resistant than polypro. Yeah I know it's yellow but that nothing a bottle of RIT dye won't fix.
The straps are a lot cheaper on the website. You can get the 12' tie downs for 1.99 which is .16 per foot and you can also buy the 15' ratchting tie downs for 2.99 each (.20 per foot).
Here is a pic of the 15' piece I got:
It's also great because if you don't own a sewing machine you can just cut the metal hook off the ends of these straps and have a loop already sewn on the end of the webbing.
I am going to check Big Lots and Walmart for cheap straps also. I would also say that flea markets would be a good place to look.