quick one - how much is instagram worth?

If you meant what your own account is worth, there's no reliable number. The online calculators guess from follower counts, which are easy to fake. What brands actually pay depends on engagement and who your audience is. And selling an account breaks Instagram's terms, so if that's the plan I wouldn't.

that figure is a valuation of Meta's business, it has nothing to do with you. what are you actually trying to work out - whether an account is worth your time?