I've bought and sold a few A5's lately, and the biggest factors are condition and model/rarity. Some Belgium guns are a dime a dozen, so will never get top dollar, and are fixed choke (unless modified by owner) so will never be big sellers. Japan guns are less common, and most have the Invector choke barrels on them from the factory, a sought after feature. I prefer the Japan guns due to the Choke tubes and steel safe barrels. They are a bit heavier, and finish is a bit different than the Belgium guns, but again my preference.
As for value, depends on the gun and the buyer. I recently sold a Japan Sweet Sixteen 16g for almost $1200. Was in excellent condition, had the Invector 26" barrel, no box, but good luck finding another one of those for sale. And the buyer scooped it up, so goes to show if you have the right gun, people will pay right price. I've seen NIB Japan Sweet's sell for $1500+ in the US. And I recently glady paid $1000 for an A5 Japan Light Twenty. This gun was stunning, in as new condition, looks like it was never shot. Had the chokes, manual, box, everything like i just bought it from the dealer. Again, these don't come aroung that often in this condition with orig box and acc. And the way I see it, going to the dealer and buying a new Browning Silver 20g would cost me more than that, and the A5 is a much better gun, so no way I was passing it up. Plus nothing beats hunting ducks or pheasant with a classic, mint A5 in your hands.
So again, with the standard A5's might not command top dollar, the condition and rarity will dictate the price paid.
