a mechanic is paid in the same way a pilot is paid. What the union negotiates. This will be between the lowest income someone is willing to do the job for and the upper end is the cost of replacing you. A union drives up the replacement cost but does little for the low cost of entry. So far the entry cost to become a A&P is less then the cost of becoming a pilot.
Its a great field and hopefully the pay will be able to be driven upwards.