How to calculate the equivalent server

Hi,

Our customer has Quarter Rack Exadata X5-2 with 6 DBs.
The owner of business want to migrate these DBs in non-Exadata HW, he is confident that it will be cheaper :(.
I need to show, that it will be very big server or 6 big servers (therefore Exadata is cheaper).

So i need to correctly calculate the number of CPUs for evaluation.
The load for every DB is coming from 2 levels:
a) DB nodes
b) cells

The load from DB nodes I obtain as:
select dbid, max(maxval)
from DBA_HIST_SYSMETRIC_SUMMARY /60-sec average/
where metric_name="CPU Usage Per Sec";