Service Contract Counter and Break Price Calculation

Hi Every one

I have one business requirement for service contract counter .We are Selling 50 copier to one of customer.Each copier already attached with counter.But our business scenario is to calculate sum of all counter in one value and provide free copier which is not base on period and when customer print all free copy from combine  of all machine then start charge on quantity of print by all printer.Example

Copier 1-- 50(Machine)

Free Copy together with all machine 100000 copy free(not base on period)

Once all machine print 100000 then applicable for charge per copier.

This is apply for bundle of Copier machine.