50 pounds for a bag of leaves sounds pretty heavy, other than weight also consider:
Can you dispose of them for free as green waste at your landfill (saving the bags to reuse if possible)? Find a multiplier for your time, what is your target hourly rate? How many bags can you reasonably do in an hour (mulch if you can, less energy spent). There is not likely going to be a set rate for leaf raking - it is going to vary according to the market and situation. It is just part of the learning curve sometimes to throw a number out there and see if it flies, just try to come by the number realistically and with the big picture in mind of the other services being done.