Posted: 19/11/2016 at 11:32
Do you mean seeds of named varieties? Not all named ones are hybrids so do come true to seed as long as they are grown isolated from other varieties. That is the result of many years of isolation and inbreeding with the regular removal of any plants which revert or are different from the desired form. More work = higher price.
F1 hybrid seeds of named varieties are produced by crossing the two original parent species and collecting the seeds. That can take a lot of manual work and the parent plants have to be grown isolated with insects kept out so all of that work makes them more expensive.
I do agree with nut though as some named varieties are not much different from the species and not worth the extra writing on the label in my opinion. I would say that if you want a named variety, buy a decent sized plant in a one litre or bigger pot.