Ah, the simple pleasures of life. Among them: booking a ticket on Southwest Airlines and discovering you've landed a position in the coveted "A" boarding group.

Now, it's been revealed just how much money the airline makes selling its EarlyBird Check-In product that increases your chances of landing that higher position: $358 million last year alone--and it's poised to go up even higher, shortly.

Southwest brought in $21.2 billion last year, so Early Bird Check-in apparently accounted for 1.7 percent of that.

Not enough to make or break an airline, true. But just imagine how your boss would react if you came in Monday and said, "Hey, I just thought of a way to increase our topline revenue" by that amount.

Not only that, but it's a digital product we're already giving away for free--and it basically costs us almost nothing to produce. (Yeah, you'd probably get a raise.)

For the uninitiated, Southwest is rare among airlines in that it doesn't have assigned seating, meaning you can choose your seat on a first-come, first-served basis when you board. 

Starting in 2009, the airline unveiled EarlyBird Check-In, selling passes for $10 to allow passengers to move up in line. EarlyBird doesn't actually guarantee being allowed to board during the A Group (before the B's and C's, naturally). But it does mean you'll be ahead of everyone who doesn't pay. 

According to the airline's website:

EarlyBird Check-In is a low-cost option giving you the convenience of automatic check-in before our traditional 24-hour check-in. You'll have the benefit of an earlier boarding position. As an EarlyBird Check-In Customer, you will have a better opportunity to select your preferred available seat and have earlier access to overhead bin storage for your carryon luggage.

I hadn't noticed this line item before, but the figure was revealed this week in reports that Southwest plans to increase the cost of upgraded boarding passes--a more expensive product that actually guarantees you'll be among the first 15 people to board--to as much as $50 per person each way in some of its most expensive markets.

(Other ways to guarantee you'll have better boarding positions: buy a more expensive Business Select fare to begin with, or travel with a child under age 6. Families with little children always can board after the A group, but before the B group.)

Interestingly, the airline apparently would not say which markets it would charge so much for upgraded boarding passes; you'll have to book a ticket and check out the option to find out.

This higher-priced product rolled out in 2013, Dawn Gilbertson reported in The Arizona Republic. The airline "started out charging $40 per person each way and added a cheaper $30 option on some flights in 2015."