I think considering the cost of change a cost of the optimized version is muddled thinking. It's a cost of deploying the optimized version, but that is only so

I think considering the cost of change a cost of the optimized version is muddled thinking. It's a cost of deploying the optimized version, but that is only sometimes relevant. A pure trade-off between efficiency and stability would imply that, were I already running the efficient version, we could buy stability by switching to the less efficient code.