They can't see it easily. especially with Commercial real estate. the value is what the market will bear and that is driven by rents. The bank asks borrowers to provide income statements and then they ask you to attest to the veracity of these statements and then they tell you that IT IS A CRIME to lie on these statements. Do other people lie, yes of course they do. And those people are committing a crime also. Banks have a slue of due diligence they can do but if you are willing to commit fraud, you can get past some of it. If you really wanted to, you could use a software program to generate a really sophisticated paystub for your residential lender that showed way more income than you really make. But that is fraud, and that is a crime and if caught, you will go to jail and or pay a big fine.How does the bank not know the true value of the property? I'm not seeing how this would work. If Trump is undervaluing his property the bank can see that easily and not accept his appraisal of it. Any research by the bank will show Trump is trying to fraud the bank. Are these banks just incompetent?