I honestly don't know how many users matrix has. I think others have already given references to estimates. Though, I believe it is vastly more than just "thousands of users"...but much like email (another federated protocol), i suppose we can never truly know that absolute number, just like we can never know with absolute certainty how many smtp servers and associated mailboxes there are out there.
I'm no longer hosting my own homeserver (can;t spare admin time for it), but when i did, it was running nicely on a $10 USD/month on digital Ocean...and this was circa 2019...I'm not an expert but as i understand it, both synapse (the python-based reference homeserver), and the vastly more performant (though beta) Dendrite have significantly improved since back then. There is certainly something to be said if you're high profile folks (like @Arathorn) who are members of tons of rooms...one can imagine that it would require more resources to support such vastly high interactions (for room data history sync, etc.)...But, hey, its early days, if the experience is too raw for you, you can wait a little while until this becomes more mainstream; no harm, no foul. :-)
I'm no longer hosting my own homeserver (can;t spare admin time for it), but when i did, it was running nicely on a $10 USD/month on digital Ocean...and this was circa 2019...I'm not an expert but as i understand it, both synapse (the python-based reference homeserver), and the vastly more performant (though beta) Dendrite have significantly improved since back then. There is certainly something to be said if you're high profile folks (like @Arathorn) who are members of tons of rooms...one can imagine that it would require more resources to support such vastly high interactions (for room data history sync, etc.)...But, hey, its early days, if the experience is too raw for you, you can wait a little while until this becomes more mainstream; no harm, no foul. :-)