Starting initially you need to buy the crimper & moding kit (if you dont plan to diy). But once you have the items, you can make your own extenders multiple times I guess. The items to make extender isn't that expensive if you calculate but you will be spending hours making it. Advantage of making own custom cables is you can specify the length yourself based on your casing (at least that is what I did for mine). If you have the kit, you can even design the sleeving based on the pattern you like unlike those ready made extenders that usually comes in 1 color.

There is pros & cons so depends on you I guess.
Thanks bro