I've had my Mavic Air since they came out - March 2018, so it's been almost 3 yrs. I have the FMC and a fair number of accessories that are
MA1 specific. I know its capabilities and limitations, and it still satisfies my needs, so I don't really have a reason to upgrade.
However, if I were to upgrade, I wouldn't sell the
MA...I'd keep it, or perhaps give it to a family member. I paid $999 for the FMC and probably another $150 for accessories. If I were selling it, I doubt that I'd get even half of that. I say this because if I were buying a used one, I would certainly not pay more than that.
A couple of points I would make about buying a used drone:
When you are buying a relatively fragile piece of electronic equipment, you are taking a chance that there may be something wrong with it, which may not be obvious to you. Even if the seller is totally honest and candid, he may not even know about it.
When you are considering such a purchase, you can't really look at what the original purchase price was. You're buying a set of capabilities. That same set of capabilities was more expensive when it was purchased, but you have to consider what that costs today. So if those capabilities were originally $1000, but now can be purchased new for $600, the $600 would be your reference point. The question that remains is how much to take off of that for wear and tear, and the risk of unseen damage being present. Consider the cost of repair which can be as low as the cost of a new set of props (~$20), or much higher, if the camera/gimbal has to be replaced.