I would think new painted 26ga. would go for $2 - over $3 ln ft.
Flouropolymer (Kynar/Hylar) painted galvalume will be on the high side with Silicone polyester painted, or straight polyester being less. In most markets, galvalume is competitive with galvanized. Some markets sell alot of "seconds", the reason may or not be visible but, it can be on the low end price-wise.
You can usually tell which paint coating you have by the amount of fade, looking at the underlap for comparison and the chalk on the surface. Depending on age and climate, galvanized can be rusted on the lower cut edge, progressing up the panel. Galvalume will generally have minor, if any rust on the cut edge. Many factors come in to play but, those are some basics.