Ya, one event I already average 20-30 GB of files. If upgrade to D800, if using compressed it will be 60-90GB... If loseless and uncompressed.. *faint*...
Estimating 30GB per event, 75MB per file, you're looking at 4000 files an event on D800.
What event are you shooting?
Of course 75 is the conservative calculation, there should be more than 4000 files per event you capture then.