Saving a buck?

I was recently approached by some project managers who were facing implementing a new database to support a third-party application. To save the cost of new Oracle licensing fees, they wanted to add the new database into an existing database system. Seems like a good idea at the time, and I could go ahead and agree being as I will not be here in the long run to deal with the side affects as I am a consultant, but would it be the right thing to do? Probably not. The right thing was to not recommend coupling an existing production system with one whose performance characterisitics are not known. Another alternative would be to run it for a few months without a license just to determine the performance characteristics to determine if it could cohabitate with an existing database comfortably, but I could not recommend that.