Another big con: blah, blah then "Get (or collect) the set" as applied to cut out cardboard prehistoric monsters on cereal packets many years ago. Also applies to many other "give away free" items but when you buy umpteen more packets of whatever, you end up with duplicates and it seems like at least one item is not available.
Spanners, socket, double open-end, combo ring + open-end, Allen keys, screwdrivers, chisels, collets, taps and dies and various other items nearly always sold as a set. Very often some items will suffer heavy use, e.g., 2/4/6/8 BA taps but 1/5/7/9 even 10 BA never/rarely used. Same with dies. Boxed sets always seem to contain tap wrenches and die stocks to add to your fast growing collection of these often unwanted items which are nevertheless included in the overall cost of a set. Look at drills – Letter/No./Fraction/Metric. Adverts try to encourage purchase of sets. Letter "F" or No. 43,27 spring to mind as commonly used ones along with no doubt a number of others for tapping sizes diff. threads but many others as new. OK, individual items can be purchased often at a much higher price.
Feel like I long ago joined the huge club of conned mugs.