Maybe not quality of the person, but quality of the job done, absolutely.
When working for free on my hobby projects, I do my absolute best. Now try to pay me $3.50 per hour for similar work (strictly +Infinity% more than before!), I'll probably flat out refuse / won't focus on it as much.
When working for free on my hobby projects, I do my absolute best. Now try to pay me $3.50 per hour for similar work (strictly +Infinity% more than before!), I'll probably flat out refuse / won't focus on it as much.