> Bitcoin holders as a group are constantly losing money by definition

Modulo market cap representing unrealized PnL, but yes otherwise. Miners and exchanges take a good cut.

Yeah the paper gains are nice, but they all net to zero in real money.

I'm trying to figure out what the significant storage costs for bitcoin are. It's a bit higher than a Robin Hood stock because it costs fees when buying/selling, but it's significantly lower than gold/silver which really require some investment in physical security or a vaulting service.

Mining and theft mostly.

It's the miners who are hemorrhaging hard currency. It's currently costing $8-10 billion per year to keep the BTC blockchain alive, but blockchain fees are paid when transacting, not when HODLing, so it's not a storage cost.

Miners get paid in BTC but have costs in money.

They have to sell, so the money is coming from buyers and impacts holders via reduced demand.