Your math is probably correct, but the logic is flawed. To keep things simple, let's use some easy-to-work-with numbers:

2018: Total hashrate 10 EH > 5 EH or more needed for a miner to attack
2024: Total hashrate 100 EH > 50 EH or more needed for a miner to attack

If you cut 2024's hashrate down to 10 EH, it would be ten times less secure than it was in 2018. Simply put, acquiring 5 EH, which was 50% of the total hashrate in 2018, was significantly more difficult than acquiring 5% of the hashrate today. The same logic applies to the cost, infrastructure, and availability of mining gear needed to perform the attack.

Acquiring enough mining equipment to control a majority of the hashrate is a significant barrier. In today's context, with a hashrate of approximately 600 EH/s, obtaining 300 EH/s worth of mining power is logistically and economically impractical due to production and power constraints. It's not just the cost; it's the production and power constraints.

The largest farms on the planet, like MARA, which runs roughly 35 EH, are striving to push that to 50 EH by the end of the year, so even the largest Bitcoin miner couldn't attempt an attack. Even with unlimited funds and support, they simply can't achieve that scale. Conversely, if the hashrate dropped to 50 EH tomorrow, it would enable companies like MARA, RIOT, Bitfarms, and others to attack the network on the go without needing to acquire more hashrate.

I also don't understand why market cap or block rewards have anything to do with this. A 51% attack on the network doesn't mean the attacker would make more BTC than they could otherwise "legally." An attacker would only achieve one of two things:

1. Double Spend

2. Damage to the Ecosystem

In both cases, the incentive remains the same regardless of the price of Bitcoin or the block rewards.



What $7? I can cut you a deal for $3.5 if the quantity is large .

So, using d5000's numbers of 2018, achieving 6 exahash cost $300 million, with the price per terahash (TH) at $100. This represented 50% of the total hashrate back then. Today, 25 EH, which is 50% of a 50 EH network, costs $87.5 million.

While the overall cost difference isn't huge, the practical feasibility is starkly different. Currently, 250,000 miners (for 25 EH) can be easily sourced from various places like Telegram groups. In contrast, in 2018, the 214,286 S9 miners needed for the same attack were simply not available. Even Bitmain didn't have that much stock at any time. Moreover, the 400 MW required to run these miners and the necessary space were not accessible to anyone.