They make the rules, and so they'll try to do that again.
Nicely put.
If they aren't interested in games they could publish a set fare for a set route. Instead they have 4 or more fare classes visible to end users and more in the backend leading to opaque unpredictable pricing, they gamify the experience using literal points and rewards, they constantly change prices, they charge fees for services that vary depending on fare class, what credit card you purchased the ticket with, what credit card you currently hold, how many times you've flown in the past year, how many miles you've flown, how many dollars you've spent to fly those miles. I'm not sure they could make it more of a game (BTW, games are not in opposition to making money, they frequently enable making more money. Exhibit A is airlines. Game theory textbooks will use them as examples).
And? They offered a $50 ticket. Did they expect people not to buy it?
If I search manually and find the $50 flight I planned spending $200 on, I’m not going to decide it’s too cheap. MCP acts the same. For at least a decade there have been services that will alert you when a specific flight drops in price, letting a human basically do what the agents are doing.
If United doesn’t want to sell a ticket for $50, then they should, y’know, not sell tickets for $50.
If airlines didn’t want to play pricing games, they could stop playing pricing games. List a standard fare for a route if you want to sell fares at a standard rate. If you want to try and squeeze me for an extra $20 because I’m buying during work hours, or $100 because I visited your site 5 days ago and now you think I’m desperate then you don’t get to complain when I use underhanded tactics to get the best deal. They make the rules, they shouldn’t be surprised when their convoluted system gets exploited by people that know the rules.