"I can understand the fees, interest and such on the amount they paid for it, but how can they claim a loss greater than thier actual "real" cost, which is usually pennies on the dollar?
Shouldn't they have to show in court what they paid for it if we ask?"
What the person who buys a debt paid for it is irrelevant to the debtor. If you owe Big Loan Corp $1,000 and default on the debt and then it sells hte loan to Loan Collection Corp (LCC) for $200, LCC can still collect the $1,000 that you owed on the debt. It is not at all unfair to you because no matter who owns the debt, your obligation to pay on it is exactly the same. Thus, in a court case where LCC sues you for a judgment, what it paid for the debt does not matter because it has no bearing on what you owe: $1,000. What LCC is required to do is prove that you owe $1,000 on the loan--if it can prove that, it will get a judgment.
This result occurs because it is a contract case, and contracts are about what the parties promised to do. If you promised to pay $1,000, then that is what the holder of the debt is entitled to get, regardless of what the holder paid for it.
If it were a tort claim (e.g. personal injury case), then the measure of damages is different, because torts are about recovering for actual losses incurred, not collecting on promises made.