Budget Travel - How to get airlines to do math

In pricing a trip from FAT to YUL, I found I saved $293 off the lowest fares by booking this way:
(1) A separate round trip FAT to LAX ($326)
(2) A separate round trip LAX to YUL ($451)
The $777 total is well under the $293 total of booking it all on one itinerary.

The question is this: Apart from the question of whether to drive to Los Angeles or fly (I have a prius, so I'm driving, I'll save $300 after gas costs), why do the airlines price this way? More importantly, if I book my flight from a small airport to the large one as a separate itinerary from the main flight between the large airports, is there any way to later tie those itineraries together? With free-standing itineraries, a delay in my inbound flight would be a disaster -- and must I simply avoid checking bags?

Alternatively, I'm sure I can just wait a few days, fares will shift again, and this price split may disappear.

Were the FAT-LAX and LAX-YUL fares on the same airline?

Regarding why the airlines do this, it is simply because some markets are more competitive than others. If they raise FAT-LAX or LAX-YUL fares, people will switch to other airlines, but fewer airlines serve both FAT and YUL, so they can charge a higher fare for that without losing as many customers. It's also a case of price discrimination. You took the time to figure out how to get between YUL and FAT for $777, while other passengers were willing to pay the full $1070. The airline got a larger profit off the other passengers while not losing your business. Mathematically a producer will always make a higher profit if they are able to separate and their customers into as many separate markets at different prices as possible.

Unrelated to the actual question, but depending on how long your trip is for, it might make more sense to take Amtrak (and the LAX flyaway bus) from Fresno to LAX ($70 roundtrip) and save the cost of gas and parking.

Edit: What dates are you looking at anyway? Beyond the next 4 days, FAT-YUL all-the-way-through fares are available for under $1000 for the rest of the month.

I was looking in October/November -- using farecompare, which is probably not the best source. In fact, definitely not the best source, since aa.com just priced FAT-YUL october at $962.

This trip will be to visit family, so dates are flexible. I'm probably going to check fares periodically over the next few weeks, I'm sure they'll move up and down (um, and not on farecompare I think).

I'd agree with the price discrimination aspect. Interestingly, it seems like once you involve a Canadian airport, price volatility goes up.

Amtrack is a good idea, except from Bakersfield to LA you're on a bus. Amtrack connects directly to the BART, though, so its a great option to connect to OAK or SFO.