"Plans sold off-exchange must offer the same essential health benefits as plans sold on the exchanges, but the primary difference between buying plans on- or off-exchange is that only on-exchange plans are eligible for government subsidies.... On average the least expensive bronze plans offered by the four off-exchange insurers were 45% more expensive than the least expensive bronze plans offered on the exchanges. [A table] displays the lowest bronze plan premiums and corresponding deductibles for each city in which at least one of the off-exchange carriers offered bronze plans."