That’s not really how this works; the cost is marginal.

Is it marginal only for best-in-the-world experts and a serious hurdle for everyone else? If so that's still worthwhile as it means the attacker must hire (or be) an expensive expert.

The bar for iOS exploitation is already one that only admits best-in-the-world experts.

Also makes the value of Pegasus increase.

Yet increases their costs to get / develop exploits