This is not being a dick. Before I left a certain job, I had my supervisor (also owner of the company) tell me exactly this. She once quit a job and did exactly this. And was proud of it. Even if I'm happy I no longer work for her, she was completely right about this move.
That's what I did and a previous employer occasionally has me do some maintenance work and are glad to pay that rate, especially if I get on it quickly.
“ If your company needs you beyond that, contract billing should start at 5x your salaried rate, 20 hour minimum.”
Now that’s being a dick. Looking out for yourself does not mean being a dick.