Sure, it makes sense. For $16, it was a great deal, and for $24, still good, but no need to go over the top. I'd say buying 3 more was fine. Don't let the numbers mislead you; don't buy something only because it is cheap, buy it if you need the parts. While that 2300 might look good on paper, in reality, you are only likely to use about half of that amount, or even less. That said, it's still a good deal.
Also, make sure to sell the other special parts (apart from the minifigs), like the blue key or the gold treasure chest. Even $1 or just $0.50 counts when you are trying to make money back.