For most skiers, untreated ski socks work perfectly well — especially if they're made with merino wool. Merino naturally fights odor-causing bacteria, so you'll stay fresh through a full day on the slopes without any added treatment. Just wash them between uses like you normally would.
The main time to consider antimicrobial treatment is if you're heading out on a multi-day ski trip where you won't have access to laundry, or if you're looking at synthetic socks (which tend to hold onto odor faster than merino). For regular resort skiing with daily washing, untreated socks are completely adequate.
Don't pay a big premium for antimicrobial treatment if you're already buying merino wool — you'd be paying for something the fiber already does naturally. Save that money for a better sock overall.