Yes exchange rates fluctuate, but the point of it is to see what your assets are worth where you are headed. Back in the day when I did my interview, and I come from a place with very volatile exchange rates, I had a USD value too on all my asset statements. An exchange rate is not going to change $1000 into $10000, and there is not much real difference 10% or 20% either way in the overall assessment. And yes people might lie but that’s true of any form for immigration, and this one has the standard penalty and standard disclaimer ... and many people have found out to their cost that telling the truth about an unfavorable fact is less of a problem than a denial and possible ban for misrepresentation.
. I understand all of the information contained in this form and I certify under penalty of perjury under the laws of the United States of America that the foregoing is complete, true, and correct. I understand that any willfully false or misleading statement or willful concealment of a material fact made by me herein may result in refusal of the visa, denial of admission to the United States, and may subject me to criminal prosecution and/or removal from the United States.