Haha, I love it. It's incredible how tables turn once you submit your resignation. I was being outsourced and my boss declined even the smallest raise, saying that his client would have to raise the payment as well, and I cannot skip him as the middleman. So I resigned and found another job. The next day client reached out to me and asked if I want to skip the middleman, because suddenly it's fine and there are no contractual problems. That would probably mean like a 40% raise at the time. I was tempted, but it was too late.
As I suggested elsewhere, that's fine but you have to be OK with them saying "Sorry to see you go. Don't let the door hit you on your way out."