Well, in your opening post you said you wanted a modern one hand opening folder. The Mercator isn't a one hand opener. I'm also not a fan of the lock bar release protruding from the handle vs having a flush lock bar and a recess in the handle to allow it to be released.
Yeah, it's not really what I was looking for but it just caught my eye.
That actually helps quite a bit. I like steels like S30V/S35VN, 154CM, 440C, M390/CTS-204P that take a toothy edge and can still shave arm hair. You'd probably really like finer grain steels that easily take a honed razor edge. Uddeholm's AEB-L is a bit lower in carbon, but it's a super fine grained steel originally developed for shaving razors. Sandvik makes several variants of AEB-L, the most common of which are 12C27, 13C26, and 14C28N. You'd probably also like VG-10 because it will take a very fine and highly polished edge with very good retention. VG-10 is more abrasion resistant than more basic alloys, so it takes a little longer to sharpen, but it does take a much finer and more polished edge than 154CM with the same or less time and effort.
I know those aren't carbon steels, but I hope that helps you to find a less expensive and more widely available folder.