While not quite the same, but will give you an idea...
If you had a pair of ball pythons, and they both ate one rat a week, without ever fasting, add up the amount of rats required to keep them for 14 years.
That's how many rats my Ornate monitor ate in his FIRST TWO YEARS.
Granted, arboreal monitors are a different varanid altogether, but that is an example of the expenses involved.
As well, there is NO STORE BOUGHT ENCLOSURE that is suitable for a monitor. Period.
Check around the internet, on many different forums, and YouTube, by entering Varanus prasinus.
Chris