in general most UV printers will use around 1ml of ink to cover a square foot of media when running 4 color work. 6 color will add about 20% additional ink. I posted a method of calculating your actual ink use under a topic regarding the ION in this same section a few months ago. If you have access to a good scale, you can figure it out on your own with a little effort.
Your milage will vary depending on the RIP you use, the profiles within the rip, and the accuracy of your color calibration. Other issues to think about are the amount of ink used to service or purge your heads, and the frequency of said purges.