I got an 8 gallon output Sears used for $25. Had to travel to get it off Craigslist. Got it home and took it apart totally to clean with Spray-9. That's 8 gallon output, not capacity. The filters are expensive but the one that came with it was servicable. I soaked it in a bucket with some acid cleaner for a while.
It takes about 2 gallons of water, and I have been really happy with it for what it is, a hundred dollar humidifier. I read all kinds of reviews on it and that just makes things more confusing, some people won't be happy with anything.
I was putting baking pans, disposable aluminum turkey pans, anything with surface area on top of the stove for a couple seasons. It wrecks the stove with water stains no matter what.
It has a feature that makes the fan run when it needs filling, until the whole thing dries itself out; keeps water from sitting in it.
I have a surplus Navy military spec human hair humidity guage on the wall hahahahha sounds gross but it is pretty accurate. It actually has strands of hair inside it.
My laundry room windows stay a little cold, and I was happy to see condensation on the inside! That meant it can put out as much humidity as I need. 30% seems to be working good so far.
So it's worth it totally to have a dedicated humidifier even though it's another appliance that needs tending!