Bellingham-Plattsburgh rt via Vegas (Allegiant):$314 ($434 with bag) + 2 hotel nights
On the dates I checked in February, Allegiant flies 2 flights a day to Vegas from Bellingham (Vancouver)!
Montreal, Twice a Week
Allegiant's new Plattsburgh (Montreal) service to Vegas, in February, is only 2 times a week. Plattsburgh to Vegas on Monday and Thursday, Vegas to Plattsburgh on Wednesday and Sunday. As you can imagine, the Thursday and Sunday flights are the most expensive.
No, Just No. No, No, No. Because No.
Allegiant won't sell you a Bellingham-Plattsburgh ticket because they don't want to. However, if you like Vegas and want to spend a couple of nights there, you can include the city as part of your transcontinental travel.
Who Flies to Vegas, Stays in Vegas
On some days, the Bellingham-Vegas and Vegas-Plattsburgh flights match up nicely (in fact, so nicely I wonder if it is the same plane). However, if it isn't the same plane, you probably don't want to gamble that Allegiant will be on time. So, "unfortunately" you will need to book 2 nights in Vegas. That's a shame.
Like Spirit, Allegiant charges for carry-on. You need a bag, but you would save $120 if you left it at home. Study the baggage policy for applicable loopholes. You'd also save $16 by using Visa Debit (although the site says US debit only, I think that is out of date).
The Little Airport That Could
The bus between Plattsburgh and Montreal is $40, return. The airport is close to town, but the bus station is next to the highway. Figure $15 each way for a taxi. If you live near Montreal, you know about the cheap parking at Plattsburg airport. From Ottawa-Hawkesbury, don't forget about the brand new Island of Montreal avoiding Highway 30 ($1.50 each way).
The bus between Bellingham airport and Vancouver is also $40, and no taxi required. Bellingham airport also has a web site, but it is not bilingual.
No Toronto For You
Although you can't use Vegas as your inconvenient hub for getting to Southern Ontario, you can use it for a surprising number of destinations. You can also use an other airline from Vegas (Normal or low cost Spirit,Southwest, Frontier). Just leave plenty of buffer time in Vegas
It's a Bombardier!