It sounds like it worked for you, at least better than all other options that you had.

This might fit into edge cases. I've used McMaster-Carr as a consumer many times, and though I might get a discount if I bought a minimum quantity, I've been able to purchase what I needed in singles each time. I doubt if there's an e-commerce site out there that will let you purchase and ship 4 screws for less than what you would pay for 200. Even at brick and mortar hardware stores you're ripping yourself off by buying 50 screws instead of 200 (or 1000). I get that you don't need them all but the price per unit is still astronomical.

I bought a bunch of defective keg o-rings that waste CO2 and emptied a keg on to the floor over night (looking at you: More Beer!). For the price of one retail kit, I put together 10 rebuild kits worth of o-rings at McMaster. In that case (5 hours of researching which $0.05 o-ring to buy), the minimum quantity was more a feature than a bug.

I can understand the annoyance for non consumables, like screws.

Meh you can't exactly get one deck screw at home Depot.