How Does a High Fork Cost Relate to the 51% Attack Threshold?

A high fork cost directly raises the barrier for a 51% attack. In PoW, the cost is the energy and hardware needed to out-mine the honest chain.

In PoS, it's the cost of acquiring 51% of the staked coins and the risk of being slashed. By increasing the economic resources required to sustain a malicious fork, the network ensures that the potential financial gain from the attack is significantly less than the cost incurred.