Upload & Sell: Off
I like the pennies idea, which wins the originality award on this thread, but I recently recalled having old, heavy chains in a bucket in my garage that I hadn't used in years. I put them in freezer baggies because they were somewhat rusty, and stuffed them in the weight bags after this. I imagine lead is going to be heavier, but things like this kill two birds with one stone: someplace to put/store pennies and in this case unused chains. It beats throwing them out if you're cheap like me (put the hoarder inside you to use). I think the bags are good for a baseline counterweight, and then one of those orange clamp on weights from Manfrotto are nice to fine tune the balance if you extend the boom out or add/subtract weight on the end due to different modifiers, etc. The whole process gets somewhat precarious otherwise, especially if you are handling largish modifiers with counterweights by yourself.
(rereading the original post, I guess OP already considered chain and is not exactly talking about a boomed studio set up, but it's a good topic to brainstorm on in general regardless.)