Same experience. I recently bought a music activated led glasses soldering kit from Amazon. I put it together with an iron kit that was 20 bucks on amazon.

Also I bought a more expensive yuhaun hot air/soldering station (name might not be exact) I used the $20 iron to solder my drone connection and it work perfectly fine with proper technique.

I cannot tell the different in build between the 20 unit and the more expensive station.

Also the brass sponge in the hakko cleaner is nothing more than a chewy boy brass sponge. $1 at your local shady gas station.