The worst thing is that they exist and have, in many cases, displaced proper ironmongers, paint shops, etc. If you want to build a DIY store I would use, everything needs to be in anonomous brown boxes, with someone at the counter who knows exactly which one contains, say a 1/2" long,
3/8" whitworth grub screw, hexagon socket and can sell me one of them.Not if they know what they are doing.
Most will buy from trade outlets at trade prices, with discounting structures that mean they can turn a profit, even if they charge the customer 'trade list price'.
Colin Bignell