I’ve flown Allegiant before. A discount airline with really cheap fares. But they nickle and dime you with lots of extra fees. Like $25 for a carry on bag, etc. They charge extra for assigned seats. They assign them when you get on plane if you don’t pay the fee at time of booking. Even if plane is nearly empty. It is $12 fee if I remember correctly.
I don’t know details of what happened on the plane. Only what it says in article. But it could all have been over $12.
That's nothing, I had to pay $50 per checked bag on United.