I left my workshop job back in august last year to go do causal site work. Alot better money and time off, work is a bit more sporadic but i don't mind it. Workshop job rang me after a month for a chat, they acknowledged that I had been doing a great job when I was there, even acknowledged I was doing the work of two people (which they wouldn't do when I asked for a payrise due to that fact right before I quit), then asked me to name my price to come back..
I wouldn't even give them a number, no amount of money will ever change or make a toxic work environment any better.
Company is now in major trouble with WHS do to multiple safety breaches and I'm currently happy as Larry relaxing in the sun, picking and choosing when and where I want to work.