Do they come out of the same factory as the shop ones?
Are they any good?

Most sellers state steel bearings like the S3.

you can get them with stainless steel if you want to pay more but if you pack with grease and regularily service then the bearings do not rust up. Have two and both still performing as when purchased and done 1000 miles so far without issue.
I would assume they come from the same factory as shop ones and e lower over heads as no shop etc perhaps not declaring earnings to tax man etc accounts for price.
they are NOT s3 definetly S8 or mine are and I bough the cheapest ones at the time.

I got a couple of cheap S8’s off merlin, thay had ropey steel bearings and weren’t as well sealed as a proper S8. You could argue they are still ok for 20 quid, I’d say you are better off getting an FSA XLII though.

lasted 3 months, wouldnt touch with a barge pole.