Not at all. The ability to publish a tweet to the world is nearly worthless to most people, but incredibly valuable to some. How much would Nikki Haley have paid, for example, to publish her candidacy for President to the world? $100,000? More? How much would Trump pay per tweet? How much would McDonalds pay? Hundreds? Thousands?

Charging commercial users a hefty price while letting normal people tweet for free is an obvious move, and makes perfect sense.