What is a definition of an opinion based question?

I got my question closed as an opinion based: https://superuser.com/questions/1604472/is-it-really-cheaper-to-use-a-windows-virtual-desktop-on-azure-than-to-buy-a-har.

While the question is clearly not an opinion based. I provided a comparison with definite numbers and come to a conclusion which contradicts the statements in the Microsoft Documentation. All that made me confused and led to posting a question, but instead of any kind of explanations or support I got my question downvoted, closed and not answered. I hope for any healthy explanation here.

Do you consider the following statement: `if we save 7000USD with one procedure, then it is cheaper compared to another procedure, which would cost us 7000USD more` opinion based? Is it opinion based to think of the 7000USD as a money worth saving? Do some moderators on Super User really think that 7000USD may be or may not be a reasonable saving?