A few questions…
What car?
Are Mr Clutch replacing the DMF or quoting on taking the chance it will be ok?
If you are keeping the car I would suggest replacing the DMF with a standard flywheel. DMFs are pretty rubbish, clever idea but rubbish. A lot of after market clutch manufacturers will supply a new flywheel hence the increase in cost.
However based on your post I would suggest going with your tried and trusted mechanic rather than taking a chance with Mr Clutch.
Just re read and if the cost is in the region of 450 you could be stuck in their waiting room for a few hours…