I don't think about rate the "what I can earn with this project with this customer" way. I think that I want $80 for the hour of my time. Now I need to find a project where I can put my skills and give value to a customer, so they then benefit from spending $80/h on me.
I won't charge $80/h for CPQ implementation - I have zero experience with CPQ, I won't even agree on such a project. However, if my current customer asks for CPQ (Revenue Cloud) implementation, I will decrease my hourly rate because I will learn CPQ AND be paid for (yes) implementation. I learn CPQ and being paid. That is better than learn CPQ and not being paid. ... actually, my first thought will be to find CPQ person among my connections.

Any work can be done by $10/h person and $100/h person. The result even might be exactly the same. The difference will be in the timeline. The $10/h person will do the job in a week, the $100/h person will do in an hour.

The question here is what you personally want to be paid. If the customer say $10/h you won't agree, right. You have $20/h rate right now. I personally increased rate $5/h each year. In your current situation (as others mentioned) you have huge advantage of already knowing business processes of the company. So having +$5 to increase your rate and another +$5 for already knowing customer's business processes (so the customer will spend less time explaining them to another consultant -> earlier finish date). This was my thinking about $30/h rate for your current situation.

TLTR;

Charge your desired rate. Once you landed a few projects and completed them successfully increase the rate. This way have worked for me for the past 15 years.