I think you are high on that price, but without more specifics, its hard to say. It also depends on where your market is. But a used clutch isn't worth much as a rule. The only info here is "low miles" which is very relative, especially for a Cummins. Some folks think 200k is "low miles" for the 'million mile motor'. But even 100k can be all she wrote for a clutch depending on who and how it was used.
And, as was already asked, exactly how complete is the package?
Used NV4500 is worth about $900 tops, imo. Block adapter $100. Bellhousing $100. T-case depends on which on it is, the DHD or DLD, but figure $400ish. Flywheel is maybe another $100.
A truly complete setup, from pedals (which he never mentioned) to t-case, in good condition, is worth about $2000 imo. Otherwise you would be better off finding an entire truck, taking what you want, and selling the rest.
All he actually asked about was the value of the NV4500 and the mystery t-case. I would say @ $1300 for those two items in good shape.