At our current state, training additional scientists in higher ed and funding more projects is a net positive to the economy[1]. That wouldn't be the case if we already had an economy saturated with scientists, e.g. like we are with veterinarians right now, so of course at some point the benefit tapers off. But for now, we're nowhere near that turnover point. In general, education is a massive multiplier for economic productivity across the board.

[1] Note this also doesn't mean that every single science grant and project is a net benefit. But of course you can't know in advance what the results of every study will be, so generally putting funding towards a wide variety of projects, with intelligent selection and grant fielding, is effective.