One thing to keep in mind about "collectible" bikes and the prices that go along with them...
The ones that bring good money are stock with no stories.
Sure for years guys saw some exhausts and other mods as a plus.
That was when they were just used bikes. Those mods added to the enjoyment and use of the bike.
Now in the collector market guys are valuing low mileage stock bikes.
Does that mean a bike like this is worthless? Absolutely not.
But you have to adjust expectations to the market demands.
Agreed.... to an extent. These bikes are still ridden, and such add-ons would also be appreciated by a potential new owner. Will some cans or a chip hurt the value? No, not in my opinion. Will it help it significantly? No. The one thing that would help the value of a low-mile Ducati would be tasteful, easily replaced mods, where the original owner has retained all the original parts. Being able to restore the machine to stock is very important, as what one person likes, may not be what another would appreciate. It always makes me raise an eyebrow when I see people trying to fetch a premium on a custom painted bike, when custom paint is about the worst investment you could do, actually hurting the machine's resale value.
All in all, tasteful mods don't really affect the value in either direction, so long as they can be returned to stock.
The exception to this of course, being the ultra rare, or ultra low mile motorcycles... (Supermonos, Paul Smarts, Mike Hailwoods, Superlegerras, Desmosedicis, and your 1, 2, or even 3 digit mileage bikes.)