I don't really agree with the original comment, but your response is worse than what you're responding to. What does what you saw in the modlog have to do with this comment? He really wasn't that mean, and raises a valid point at least. You could've just said "We should've checked but it's still a fun topic" or something that acknowledges the mistake but moves on anyway.
Also, if it costs money for people reading it, why would you share it? I assume you shared it because the cost is worth the price of sharing something you enjoy, but if that's true why bring up cost at all?
Btw, it's a bit cliche to respond to criticism with the sentiment of "I'd like to see you do better" rather than accept it for what it is (assuming there is validity to it).