Unless you need to control components, velocity, etc., it's not worth the investment in my opinion. Reloading obsolete or difficult to source cartridges is economical....if you shoot them. I'd hate to buy 450-577 Martini Henry or 8mm Japanese, or even 30-40 Krag. If I'm using cast bullets, I can load for a fraction of the cost of new. I think .357 Sig is still commonly available, my earlier joke post aside
I agree some rounds aren't worth the trouble but if you already have the equipment then 357 sig is worth it.
Lot of rifle rounds are worth it too, but 9 really isn't especially the target rounds which I've bought somewhat recently at 20 cents a round.