depends on the bike….
XC racy/Road thing ~380g
Traily thing without dropper ~480g
Traily thing with dropper ~750-800g I guess, not actually sure!
Touring thing with big leather saddle, who cares when it has KG’s of bags strapped to it!
Some OEM seatposts can be surprisingly boat anchorish, a decent carbon one will be <200g, (and there are some light scandium ones near 150g too), but I once had an OEM Specialized post in one bike that weighed nearly 400g 😯 ,same with saddles too, but I’d only change the saddle if I was happy with the comfort of the replacement, no point saving 200g* but being in agony!
You might find a lighter post is a bit more comfy too though if you get a bit more flex and spring out of it, so it might be a double upgrade in that sense, do you have a particularly fussy bottom when it comes to saddles?
*arguable if it’s worth it at all 😉