system
Given the following post, respond as if you're commenting on Reddit:
human
I believe the ISS has been a complete waste of money. CMV

I accept that there have been valid scientific advances made with the ISS, but not nearly enough to justify the ridiculous price tag. 

Can anyone name one single major achievement the ISS has made?

Furthermore, a significant number of the tests done could have been carried out by unmanned probes. 

Of course whether a science experiment can justify its budget is always going to be subjective, so the best way to deal with this is to use relative measures:

At $150bn, the money spent on the ISS could fund the entire University of Cambridge for over a century. 

The LHC costs less than a tenth of this and has achieved much more (I know that's subjective- but how many new particles has the ISS discovered?)

You could build and run hundreds, if not thousands of hospitals with the money.

CMV!
gpt
Iss will be invaluable if we ever decide to send people to Mars or similar as this is the only place people have lived over a longer timeperiod in zero gravity ( well that and Mir ). If sending people to Mars is a worthy goal is up for debate of course. It is also practice for setting up and supplying lunar colonies, which could actually be comercially viable for HE-3 extraction. 

Basically it is like saying the planes the wright brothers built were a waste of money. This is our first attempt (second if you count Mir) and the lessons learned are enormous for future space exploration and colonization. 

This is in addition to the direct scientific discoveries from the only functional micro-gravity lab in existence, which is invaluable for nano-manufacturing, biology, chemistry and a host of other sciences and industries.