Porrohman, no doubt you are in part correct - from a bean-counting point of view.
However I am a pilot therefore I support anything that keeps airports open. I was born in Dundee so I particularly want to see Dundee kept open. To me there are few better ways of spending public money.
The pax figures you quote are from early 2013. Check the numbers in 2012, 2011 etc, before the development projects in Dundee started in earnest, and now think about what could be achieved in 2016, 2017 when they start to bear fruit. Be a shame not to have an airport anymore wouldn't it?