Cheapest would be- Costco,wallmart,Canadian tire. I have gotten cheap tires for an old car from national tire wholesale on river road in delta but sizing in certain brands was limited. I got tires for my truck before from dueck on marine but now own a new jeep that will need new ones soon here. I was thinking of driving state side getting them and coming back.
I bought my last 3 sets of tires from Costco. Busiest times are during winter and spring change overs, so if you can wait another couple of months, lineups wouldn't be as crazy unless you go as soon as the doors open.
Otherwise, you can buy online ie. tirerack.com, ship to a parcel pick-up location in Blaine/Pt Roberts and get a service shop to mount and install for you. Probably the greatest savings, but more hassle.
Depending on tire size, make and model, there may be very good savings had if you buy them off tirerack.com and ship to Hagen's of Blaine or so just across the border. Customs never charged me anything on tires and I got last 3 sets from tirerack at substantial savings, had them mounted/balanced at Tireland here in Canada at $15/per tire while paying with cash.
Currently waiting in Bellingham, getting a set of performance tires installed at Discount tires. If you don't mind the hassle, they will pricematch. I'm probably saving at least $400 on a set of Hankooks.
Costco is good if you want the tires that they sell but their selection is limited. If you know what you want and want to drive to the US, go with tirerack.com or discounttire.com. If you want to get it done locally because of time, I like Victor Wong at Tire Town on Hastings street. He's done 4 sets of tires for me. But once again you have to know what you want as he will quote on what you ask.
Are you looking for used or new? If you want used tire, there is a guy in Surrey who sells used tires and his is pretty cheap. His price includes installations and mounting and tax.
They are called Used Tires Surrey.
I am not sure if phone number/web site is allowed. If they are not, please remove them and accept my apology.
604-506-9362 Used Tires Surrey Langley Burnaby Richmond Vancouver
I just put a new set of tires from Costco on my minivan; Richmond was crazy busy, told me I was looking at 4+ hour wait time for installation, or maybe even would have to come back next day. I took a gamble and drove to Burnaby Costco. Way quieter. They had me in and out within an hour.
I now go by Burnaby Costco whenever I am in the neighborhood. It is so much quieter/peaceful than the downtown Vancouver or Richmond stores. Bad for their business maybe, but a way better shopping experience.