I know what you mean. But there are two things to consider:-

1. The effort it would cost to start from scratch on a new platform. (I already did on Fiverr FYI) as I have a stunning Upwork profile.

2. The legal aspect If I just decide to "shut down" my account. I'd believe according to them, I'll still have to pay this sum.

I don't want to pay back the $12.5k, but one has to think of all the options.

1. Paying back over time and resuming work there.

2. Not paying back and building a new profile from scratch, which would take effort that could be worth more than $12.5k.

I agree with you in everything you said though.