They might need to have seats on that flight offered to meet a contract with the airport, or they might be using personalized pricing to only offer the 50 dollar price to certain customers (if you keep searching often the price goes up for instance) or any number of other stuff. Airline pricing is like car pricing.

No it is not. Cars have static MSRPs and then you haggle over the price person-to-person at a dealer. Airlines prices are based on markets (literal demand and supply between city pairs,) expected load factor, and what can best be described as a min-maxing algorithm to minimize spoilage (% of unsold seats when the flight takes off.) It's all predictive analytics, constraints modeling, and optimization at scale while finding opportunities here and there to maximize within local factors.

Contractual discounts--which corporations do have--are usually balanced by a guaranteed spend figure. For small and midsized companies, the spend is often paid in advance, to the benefit of the airline, which can carry the float and lock up a portion of market certainty.

My two cents: I have a deep amount of respect for United's tech stack. It is the best amongst US airlines and among the best in the world. However, this is the wrong move for them, and unless other airlines follow (doubtful, since United taking the lead here gives others competitive advantage,) United will have to backtrack in a year or two.

I don't see why they would _ever_ prefer an unsold seat unless:

* they are trying to artificially inflate the price

* they could send cargo that is, per pound, more lucrative than the cost of a ticket

It's not like the weight of a person is going to cost an extra $50 in jet fuel

There's a surprisingly high price floor on airline tickets. Like $30 (one way) in fees to the government and the departure airport. Plus the incremental fuel [0] and any complimentary consumables, etc.

Not much of a factor on more expensive fares, but for short flights where a $50-100 fare is realistic.

[0]: even with today's oil prices, the extra fuel is only $20-30 for a transcontinental US flight. negligible for short flights.