With the caveat that there may be other areas that I'm just not familiar with, a few avenues I've encountered that can ultimately net you $150k without necessarily being in NYC/DC:

Corporate or high stake trial paralegal - You'd be the go to trial person. You'd step in before trial and get everything ready and ultimately run the trial when you get to it. High salary + OT would get you to $150k.

IP paralegal - You can get to $150 on salary alone but this would require you to truly understand the area and possibly have a science background.

Corporate/securities/benefits - You could get close to $150k in-house but you'd essentially need to have experience with stock plan administration and sec filings

Commercial Lit paralegal for a busy firm - You'd potentially be able to lock down $100k salary and would have to have enough OT to get the other $50k

Tying yourself to a profitable partner who moves to biglaw - You'd then need the partner to bring you and secure your salary.

You will likely run up against people who just see this salary as far too much for the position so you'll need cover. In order to avoid/navigate this issue, the firm needs to be quite profitable and you'll need to be working with someone who makes solid money for the firm who likes you and needs you.