Picture from the BBC series "Detectorists".
Because of this (and quite understandably) the rewards for single finds are often not very high, Usually in the tens of euros for a common medieval silver coin or maybe some 50 euros a gold coin from the beginning of the 18th century that was found in a ploughed field with no historical context (below).
Whats it worth?
My question is why these rewards are paid in the first case? Valuable historical objects from a historical contexts belong to the National Museum, end of question. Donating these kind of finds without compensation should be the rule.
Paying rewards for obvious stray finds (in my opinion) simply constitutes bad economic judgement (even if the general sums are small) and only serves the purpose of yearly debates about the economic "value" of the priceless faint clues into our common heritage.