Is LinkedIn Premium Worth It for Getting Clients?

if you can find the premium at a discounted price then it is good. i have linkedin premium vouchers if you are willing to try premium. for business premium i sell at $90 for 12months linkedin business premium

I would invest in it if I were doing active prospecting, but only for a short time and if I knew it would pay off.

Linkedin Premium is not magic. It is useless if you are not credible enough for any client. Use this only when your post getting some tractions, you have some active and engaging followers. Then this will give your profile some credibility and then Linkedin premium become usefull. Until then focus on your content and brand building.