You don't need to be EE-educated to know the basics about components.
I've done this with people working for me and it takes very little training. Basically you need somebody with a reasonable brain; they can learn different kinds of resistors in the same way as they could learn different kinds of screws if working for a fastener shop. It is just a willingness to learn a bit about the job one is doing. It makes life a lot more interesting, too. Most people hate their jobs these days and this is a way to make it a lot less tedious. Not a fashionable idea these days, I know

The resistor example is actually a good one, because a particular P/N, say 10k 0805 1% P/N XXX might be 0.0012 (50k+) one day, and if you reorder that same P/N 6 months later it might be 0.0150. That is about 12x more expensive. I can't tell you why this happens, but it does. The pricing on these very cheap parts just varies pretty randomly. Maybe the distis do this in the hope that the customer won't notice. If you look at say mouser.com, which has a very good clear website, you see these huge wild variations with passives. It makes one wonder who pays 0.015 for a resistor, but clearly some do. Just looked and I see them for 0.003 to 0.153! And the 0.003 is still 3x the price it should be but you have to use another source for that, and it will probably be a Yageo part.
If one is building less than say 100+ then one can get everything from Mouser or Digikey, or even Farnell or RS. Well, except pricey stuff like £10 CPUs which will be a lot cheaper from a disti. But for 1k+, no.
Distis
do make a nice margin, BTW. I have seen some real volume pricing which big OEMs get. I have a big customer which buys from the same distis I buy from, but in much bigger volumes (probably 100k-1M). Look up the price of a HCNW4503. I buy them 5k-10k, and normally pay about
£0.60.
Just very rarely I got them for £0.40. Now guess the disti's
buy price. I can tell you because I have seen their bottom
selling price:
£0.28! So they buy it for less than this. Even allowing for manufacturer price support, the margins are
huge. If you buy from say Future, Avnet, Arrow (Arrow is pretty well dysfunctional here in the UK), etc, 1k+, they are making at least 50% gross margin.