That is a rather interesting spin on things. I think if you offered them twice their wage it would depend on the effort output you were expecting of them in their current labor job. If it was roughly same output I would most definitely think that a majority would stay working hence the idea of manual labor work to begin with.
I'm not sure if they would leave or not tbh because the reward model is the $$ for work/effort. Granted at times the biggest part to many of our successes is a more bigger picture and have a lot more moving pieces like a sense of purpose so to speak. Many manual laborers do many repetitive tasks so I suppose it just depends what sector they are coming from. I.e. someone that digs trenches for pipes would probably continually do this.
Also interesting tarazkp on the study of toys, but see I think in that scenario is also a bit different although interesting to note. That is what I meant above about a sense of purpose vs just a random act of a job. I think that's why some corporate practices is to do group volunteer work to create the team environment and the feel good feelings.