We already had a post about the importance of the number of the machine needles in order to have a better fitting and comfort. But how understand how many needles had the machine, looking at the sock ? Very simple, just count the numbers of stitches on one side of the sock when is flat (before wearing it) and double it. It is actually 1 stitch = 1 needle.
260 needles it is usually the highest you can find today.
Another matter it is the gauge, which is the number of needles you have in the machine in 1 inch lenght.
Why a sock made on these high needles machines is more expansive ? First, of course, because the yarn used must be the finest, second because these machines are running slower and are more subject to controls.