If that's $5 Billion with a 'B', that is a lot of R&D. More, for example, than one can usefully spend on R&D for that topic. There are only so many qualified employees and only so many projects ready for focused R&D, in a field that is still more aspirational than anything else. That seems like 1 or 2 orders or magnitude more money than you can usefully spend. Someone will find some way to spend however much money you throw at them, but $5 Billion seems way too high.
Counterpoint: Meta is rumored to have 3 or 4 headsets coming down the pipeline for the next 3 years, and those headsets need mass-production research, games, firmware, OSes and more. Yes, it's a lot of money. Once you consider that a lot of it is going to fund game studios and thousands of software engineers, I don't think it's a terribly far-fetched figure.
They lost 3 billion in Q1, and 5B since in all of 2022, so that's pretty much a billion a month. Let's assume they have 3000 employees working exclusively in Reality Labs with an average annual salary of 200k per employee. 200k a year rounds up to around 17k a month, times 3000 comes out to around 50 million dollars a month, which is 5% of their monthly spending. Even if they were spending $500 million every month just on outsourcing/parternships (unlikely), that still makes personnel costs around 10%. I just can't imagine where all that money is going.