Ah yes... the "Mexican Hat Dance." A fun and profitable way to stick it to the airlines. And like a lot of things nowadays, we can thank the charters (Royal, C3000, etc) for it.
Mexico is a very popular tourist destination, especially for western Canadians, so there lots (and lots) of el cheapo flights. And if the large carriers want to operate these routes, they have to meet these stunningly cheap fares. So here's the deal:
1. Find a close-by yet international destination, preferably with a lot of leisure passengers. It should be a major centre or airline hub.
2. Find out who's hub is near your intended city -- DFW=AA, LAX=UA, ATL=DL, IAH=CO, etc., and pick a carrier.
3. Determine if your selected carrier flies between your intended city and proposed international destination. If not, pick another city, carrier, or international destination, and start again.
4. Hit the web, and start experimenting. Travelocity is excellent, because you can use the "Fare Listing" option to get an idea just how cheap it can be, and then you can use "9 Best Itineraries/Multiple Destinations" and start experimenting. The example I used above came with a fare of $1442CAD including taxes for YYZ-MEX-LAX-YYZ on AC for the first and last leg, and UA in the middle on MEX-LAX. Note that the first segment was in J class, but the returning 2 segments are actually in F class, for a 50% COS bonus. (For 4$ less, you can go to LAX first and holiday later, again with a mix of J and F class.)
I've done this several times, although not through LAX. My travels often take me to the Gulf Coast, so I get myself to DFW, and take short commuter (read "cheap") flights to, say, Houston or New Orleans. And while I would like to have taken a short holiday, my schedule pretty much precluded it this year.
Therefore, I flew DFW-MEX, cleared customs/immigration, got back on the same plane, then spent the rest of the return flight convincing the crew that I wasn't (completely) insane. All this happened on AA of course, because of upgrade stickers, Q-miles, and lounge access. Now it will probably have to be Mexicana and AC.
(To give you an idea of the savings -- YVR-DFW-YVR, unrestricted Y = $2700, YVR-DFW-MEX-YVR in F = $1600, or minimally restricted Y for as low as $600. You also pickup 2000-3000 Q-miles, depending on COS, which were critical to me this year. All for 6 hours on a Saturday, which would have been "dead time" for me anyway.)
There are other variations as well. There's the "Flying Dutchman" -- YVR-LAX-YVR-HKG-YVR-LAX-YVR (upgraded on the YVR-HKG-YVR portions thanks to Black CP SWA stickers) for about $800CAD and a lot of tranquilizers (must be done on certain days of the week and non-stop [i.e. no "stop-overs" due to day restrictions], but it may no longer be available for that price.)
There's the "Costa Rican Connector" -- YVR-DFW-MIA-SJO-MIA-BOS-EWR-DFW-YVR. About $200 cheaper than YVR-BOS-YVR, for unrestricted tickets. But think of the miles. Good for those end of the year "will I make it" mileage runs.
And finally, "Sloppy Southwest Seconds." (Ahhhh, discount airlines. Is there anything they can't do?) Use the Southwest effect by figuring out which city near where you are now is served by WN. Fly there. Then fly where you were really going. Do it all on one ticket if you like, it won't make a difference. For example, DFW-RDU-DFW unrestricted Y is about $2000USD. On the other hand, DFW-TUL-DFW-RDU-DFW-TUL-DFW unrestricted Y is about $600. My employer saves money, my client saves money, and I pick up an additional 2000 very important Q-miles and meet and astonish flight crews, all for about 2 hours on each end. (Did I mention that I'm a blue collar hourly paid type?)
It's just the old fly Saturday for the discounted fare and get paid for Sunday routine. We call them "Forced Rest Days." Paid salary, expenses, and absurdity of absurdities, extra "field pay" for being out of town. And it's worse (better?) for a lot of overseas destinations, where the Saturday night requirement is replaced with a 7 day minimum. Ever had to go to Hamburg to do 5 hours work? I've had 4 day fully paid "holidays" in Bangkok, Germany, etc., and in each case employer and client saved thousands of dollars.
So as you can see, the shortest route between any two points is rarely a straight line. More is less, and less is more.