1. Airframe is near the end of it's lifespan.
2. Engines are near the end of their lifespan.
3. No one wants to buy an A380 so they are trying to get the price low enough to move it.
I know nothing about how to evaluate aircraft listings so it would be interesting is someone here with more knowledge could shed some light on this.
One of the engines has only 800 cycles; the others are around the 3000 mark (so roughly 300 flights/year, which sounds about right for an A380: they service long-haul routes).
It might be a case of (3), with the added problem of there being a glut on the market due to the availability of newer, less maintenance-intensive wide-body twinjets with >400 seats these days (Boeing 777X, Airbus 350)?
I think the price is low because the market for the plane is small, as is used serviceable material demand. (That’s when you strip a plane and sell its parts.)
Passenger airlines are moving away from behemoth airframes to more modern, efficient widebodies such as 787, 777, A330, A350. Freight carriers don't enjoy the restrictions that come with the A380, conversions to freight-only are expensive, and the extra load capacity isn't as useful as it might seem for standard routes. The A380 finds itself in a position where the available market is very small and getting smaller by the day.
(tl;dr; version: The A380 was well-optimized for a future that didn't happen, but not for the one that did.)
"One reason that the A380 did not achieve commercial viability for Airbus has been attributed to its extremely large capacity being optimised for a hub-and-spoke system, which was projected by Airbus to be thriving when the programme was conceived. However, airlines underwent a fundamental transition to a point-to-point system, which gets customers to their destination in one flight instead of two or three. The massive scale of the A380 design was able to achieve a very low cost for passenger seat-distance, but efficiency within the hub-and-spoke paradigm was not able to overcome the efficiency of fewer flights required in the point-to-point system. Specifically, US based carriers had been using a multihub strategy, which only justified the need for a handful of VLAs (very large aircraft with more than 400 seats) such as the A380, and having too few VLAs meant that they could not achieve economy of scale to spread out the enormous fixed cost of the VLA support infrastructure.[141] Consequently, orders for VLAs slowed in the mid-2010s, as widebody twin jets now offer similar range and greater fuel efficiency, giving airlines more flexibility at a lower upfront cost.[142][143][144][145]"
The A380 being launched right before the economic crash of 2008 certainly didn't help. It easy in hindsight to think Airbus was wrong designing such an aircraft, but that's what the future looked like back then. There's no way they could have predicted the economic shifts the airlines went through. I guess they were just unlucky, bad market timing.