I've heard good things about Mothers pure carnauba (they have one with cleaners, but I'm talking about the pure one)--paste. I've seen it for $23, and I don't know if I'm willing to pay that--or if you are.
I've never tried 3M's protectants--but if you're not happy give them a call and tell them, they usually will reimburse you.
Yes, i'd pay that much. But not unless i know it's gonna work great. And from the widely varying opinions i read about waxes here and elsewhere, i don't know how i could know for sure. Maybe companies who know thier product is great should offer sample packs for a couple bucks so you could see if it's worth blowing a wad on.
As for the idea about calling them, good idea. I've done this before with other products and a few times been shocked at what they did for me. I once complained about an $80 electronic gadget that needed a part that was impossible to find because the maker had the parts custom manufactuered for them and couldn't provide the part for me. When i complained about that i soon recieved another one free of charge and then had 2 of them ! (the broken one still worked, but was just a bit of a hassle to do a certain setting)