Thanks for this info! I was wondering if I bought a stainless steel if I’d be able to re-use the cost different in the future but several hundred down to 20 is not a good deal. They really should increase that. I can pay $125 on top my series 3 aluminum to get a series 4. But for someone that tried that upgrade as a stainless steel, it would cost them more like 400/500 after the trade in.