I have an Eco-Canteen, and another, slightly smaller no-name SS bottle. The knockoff was a disappointment, because the air-valve was stuck. I removed the silicone rubber piece, and lost it, so now it leaks if I lay the bottle on it's side. Furthermore, the knockoff brand was slightly smaller in diameter, so it does not stay tight in it's cage... Which led to the bottle popping out and landing on asphalt. At first, it only looked dinged, but when I got it home, it would not stand striaght on the countertop, next to the sink. The bottom was now bulged out. I made a temporary fix by pounding the bottom back in , with a hammer.
The Eco Canteen is on sale at CVS, for $4.99, and I plan to buy another one.
The stainless seems to reflect sunlight, so the water stays cooler, for a longer time than a plastic bottle. I would like the plain stainless, and not colored.
I don't know how you can make a bottle cheaper, but good luck with your business venture.