Warner 490 razor blade holder

Above, a tool made to hold safety razors.

U.S. Patent 3,996,665 was issued to Douglas B. Malchow of Minneapolis in 1976 and assigned to the Warner Manufacturing Company of the same city.  Founded in 1926 the company is still around, now apparently out of nearby Plymouth.  A handy way to use old razor blades that had become too dull to shave with, but still sharp enough for shop use. The tool is still available, with prices ranging from $1.98 to $34.33.  Seriously, there's this much variation on the marketplace.  Why?

I thought safety razors had all but disappeared in favour of disposable multi-bade ones.  Turns out, they're enjoying something of a comeback.  See, for example, the Rockwell safety razor, which began with a Kickstarter in 2014.  They sell their razor blades for 10 cents each!