I could add even more. Applying the specialized equipment it is possible to restore the old info that were repeatedly wiped over and overwritten by new data. This is because the heads of any HDD are not remain perfectly positioned every time the plates spin. Generally speaking the reliable destruction of data HDD holds is a challengeable problem. That is why such erasing scheme scheme as Gutman, USDoD 5220.22-M, Shneier and some others were developed.
That may be true, but the difficulty of doing such is quite extreme.
It also would depend on how many times the disks spun over the overwritten data, and the reliability
of the positioning between each spin. Depending on the manufacturer, there would be higher/lower chances
of recovery.
Data recovery for a hard disk can be near a grand for mechanical failure, for a normal disk.
Overwritten data will cost quite a bit more to recover, require much more specialised services,
and has an even lower guarantee for success.
If a person really lost a significant amount of early bitcoin, they could attempt such recovery -
but then you run into all sorts of additional issues. The data would likely be unencrypted, and I
imagine that recovery centers have all sorts of reporting or checking that they do to prevent
themselves from legal trouble.
A user that attempted such a recovery would have a hard time keeping their bitcoin if successful,
and it's not even clear that such a thing would be successful -- especially because it depends on the
number of rewrites.