What you need is justification for the new value.... ie: appraisal.  

There is NO justification for what you did, and to continue trying to justify bad behavior just makes you look worse.

They do vary over the years, and "ALWAYS" includes years that have high interest rates as well as low ones.Of course, it is hard to make a point in a discussion with someone who simply responds "If 20% mortgages are common I'm sure I can do well with my $800, 000." without explanation or justification.

It's not that I'm unsympathetic, just if you're moving somewhere and you already know the situation, then you should have the means to pay rent.

When someone tells me to replace a toilet, I need some justification.

You are now doing the same "not reading" that you accuse (in some cases with justification) others of doing.  

Then there's no question of amount of profit justification.  

The other justification to ask for credits is if it costs considerably more then expected for some reason.   

It was the advice given to me by the Maryland real estate attorney that I work with, and his justification was the liability protection is well worth it in a litigation happy environment.

I see a lot of justifications here about raising rent based on "being a business".