NO ONE said anything about cheating...at all.
Then I don't see what the problem is. Market value is typically where the bidding stops. It can typically change over time, and is most definitely a range of values, rather than a specific cut-off.
The transfer compare provides information about the approximate sales of similar players. It's designed to prevent newbies from spending too much on a player when they're not quite sure how much a player is worth -- not to be a surgical-precision tool of assessing a player's market value.
"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve."