In my opinion it matters not who owns it or even found it. A landowner's/finder's reward should relate to the items true value rather than say just a token gesture. I certainly don't expect to be paid for the often many hundreds of hours of fruitless searching before finding a treasure item, but is merely asking for a fair valuation so unreasonable?
The TVC originally under valued my gold filigree dress pin head by comparing it the same as a copper/alloy one - so were just taking the piss it seems! So I presented them with some of their very own previous valuations which they could hardly dispute and they then offered double! It hardly inspires confidence but I will keep an open mind of their next valuation when it finally happens!