I don't have the financials, but I expect that after spending $2 billion for the acquisition, they didn't live them alone.
One notable thing is that Oculus hired Michael Abrash just following the announcement of the acquisition. With John Carmack, who was already there, they are among the most (if not the most) prominent developers in the field. Even though Carmack stepped down as a CTO, both are still there. I have stopped following VR news but Oculus had pretty nice prototypes a few years ago which combined eye tracking, foveated rendering and varifocal lenses, all addressing fundamental problems with the current generation of headsets.
Also, even though I am not sure about Facebook involvement, they financed some of the best VR games at the time. Lone Echo is one of them. Ready At Dawn, the developer is now part of Oculus Studio, a branch of Oculus focused on making VR content. Note that having good VR content is extremely important, even more so than the devices themselves. I mean, you are not going to spend hundreds of dollars just to slash cubes, or maybe you do, can't blame you ;)