Around $150 million was spent searching including with high resolution sonar[1]. But obviously nothing was found. The area they're searching is far larger unfortunately.

[1] https://en.wikipedia.org/wiki/Search_for_Malaysia_Airlines_F...

The precise location of the wreckage nonwithstanding, the fate is pretty clear. Several pieces of MH370 have been discovered washed up along the coast of Africa and Madagascar over the past few years.

A company, Ocean Infinity, is continuig searching with robots.

iirc when it was missing there was a lot of wild speculation and then someone (maybe it was on twitter) discretely said it was on the bottom of the ocean at some location i can't remember and nothing else. The conclusion was this person was from some three letter agency and knew exactly where it was because of all the listening devices in the various oceans hunting for submarines. They(agency) will never say where it is because it exposes their capability. I think a similar thing happened when that submarine imploded on the way to the titanic.