Your right about the cost per wrap being the same. I know people that have used 1.5 wraps on alfalfa with no problems, and I've done grass with 2 wraps and corn stalks with 3 wraps, which is less than recommended. The pressure setting on my New Holland is at 2050 psi, which is near the upper limit, and I never had a bale explode. I suspect the sellers just want to sell more product, so they recommend more wraps. I've also used Tama before, and it worked OK, but Tama is made in Israel, where Pritchett is American made, and it weighs 15 pounds more then the same size roll of Tama.
How long will the wrap survive out in the sun? I've never had a bale outside for more than 8 or 9 months, so I honestly can't answer that.
Paul N