Depends on which companies we're talking about. Nvidia's annualized operating income is so high right now that it'll be capturing more value (op income) in the next four quarters (~$120 billion) than its R&D expenditures have cost over its 32 year history combined. For Nvidia the return has long since been achieved.

As the AI spending bubble gives out, Nvidia's profit growth will slow dramatically (single digits), and slamming into a wall (as Cisco did during the telecom bubble; leading up to the telecom crash, Cisco was producing rather insane quarter over quarter growth rates).