Have flown to Spokane a couple times, and the flight was always $400. Of course, I only fly with Delta and take only a carry-on since the carry-on is free. Not a checked bag person here- unless it’s absolutely necessary and that last time was a trip to California.
Also, I have purchased tickets only on Expedia since it’s a bit cheaper. Delta website is $200 more. If you move dates around, the prices do vary.
In preparation for an upcoming biz trip, I priced a trans-Pacific itinerary on the usual online sites (CheapAir, Kayak) that do a meta-search including Expedia. I compared the itinerary with AmEx Travel and, while there was some give and take on the various legs, the overall cost on AmEx was several hundred dollars cheaper.… PLUS… because I booked online, AmEx offers a special travel insurance that includes medical coverage overseas, evacuation costs, and even full refund for cancellation for any reason within 48 hours of departure.
It was only on the trans-Pacific legs that there was a significant cost savings. For the "in-country" legs it was a wash, prices within a few dollars of each other.
When it came to accommodations, Agoda was significantly cheaper on all bookings except for one. AmEx saved me about $600 on that one because it was with one of AmEx's contracted "Hotel Collection." Agoda also had the advantage of offering a variety of options: pay now, pay by, and pay at the hotel.
It's a pain to spreadsheet the flights and hotels, but doing so saved me about 25% of the expense. Well worth the effort.