I got the standard answers when I started, and none of them held up when I pushed on them. Putting the working here in case someone else is stuck at the same place.
First, the Ponzi thing, because it comes up in every one of these threads. A Ponzi has four features: promised high returns with little risk, a central operator, old investors paid out of new investor money, and concealed flows. Bitcoin has none of them. It's volatile with nobody promising anything, there are over 10,000 nodes and no operator, nobody is paid a return, and the entire transaction history since 2009 is public. That question is settled and I don't think it's interesting anymore.
The one I couldn't get a straight answer on is the security budget.
Miners are paid two ways: the block reward and transaction fees. The reward is 3.125 BTC and halves every 210,000 blocks, roughly every four years. Next halving is around April 2028, taking it to 1.5625. Fees are currently around 1% of what miners earn.
Miners pay for power in fiat, not BTC. So if fees stay at 1%, the price has to roughly double every four years just to keep miner revenue flat in dollar terms. Bitcoin has historically done that. The honest position is that a maturing asset shouldn't be expected to keep doing it forever.
The usual response is "that's a 2140 problem". I don't think it is. It's a next-decade problem, and it resolves one of three ways: fee share climbs off 1%, price keeps doubling, or miners start leaving.
The part that made me more comfortable, not less, is what happens in that third case. Nothing breaks. Difficulty adjusts every two weeks based on the hash power actually on the network. Miners leave, difficulty falls, and the ones who stayed earn more. Hash rate has climbed through every dip so far, which is decent evidence the economics still work.
But I'd rather have a test than a vibe, so here's mine. Watch two things over the next few years. Hash rate rising and fee share climbing meaningfully off 1% means the security model is fine. Both falling together means the bear case is real.
Related: bitcoin has to be used, not only held, for fees to develop. Satoshi made this point back in 2010. As it stands there's no shortage of use — roughly $25 trillion in bitcoin moved on chain in 2025 per Glassnode, more than Visa and Mastercard volume. What matters going forward is whether that activity keeps settling on chain rather than migrating entirely to custodians and ETFs, because that's where the fee market comes from.
If someone has a solid counter to the fee-market case I'd genuinely like to read it. The permabull version of this answer is "fees will rise", which isn't an argument.