Following the draft an awful lot of meat (rookies) goes on sale, often for very low prices. There are often so many of these that people are able to pick up high potential players for low prices. For example a HOF potential 19yo might only go for as little as 16k.
Some unscrupulous people buy players like that and try to sell them at vastly inflated prices, hoping someone might not notice how high the price is that they're paying. That same 16k purchase might be advertised for, oh, lets just pluck a figure from the air, we'll say perhaps 150k. Clearly in, however many days might have passed since that purchase, lets guess about 10 days for the sake of argument, he can't have increased in value 10x. Certainly whatever training he may have gotten, and lets face it, he probably hasn't been trained, has not increased his value. Or, metaphorically, the price of meat doesn't change much in 10 days.
In summary, what I'm saying is: CHECK WHEN A PLAYER ON SALE WAS LAST BOUGHT AND FOR HOW MUCH BEFORE YOU BUY.
Any resemblance to actual events or locales or persons, or BB players on the transfer list, living or dead, or even fictional BB players with a meaty name, is entirely coincidental.