You're answering the wrong question. "Which of these fixes more migraines per dollar" is a fast and frugal heuristic, but it doesn't answer the question of which you should purchase.

(If the first three wheels of your new car cost $10 each, but the fourth cost $100, you'd still want to shell out for the fourth, even though it gives you less wheel per dollar.)

In this case, the question you should be asking is, "is it worth another $250 a year to prevent another 20 migraines?", which is overwhelmingly worth it at even a lower-class time-money tradeoff rate. (The inability to do anything for several hours costs them more than $12.50 in outcomes- not to mention the agony.)