The $293 tango fare is a competitive response to WS, just as the flex fare is also a competitive response. I was able to recreate the tango vs flex price variance on July 7th YYZ-YVR on AC.com. Enter the same parameters on westjet.com and found that for comparable flights times, AC and WS are price matching each other.

With Westjet transitioning to the fare bucket approach, the difference between fare buckets will make less sense than when AC had fare bucket unto themselves. Also it was Westjet that introduced the concept of only offering seat sales on the lowest fare bucket (econo in WS terminology). WS also closes off lower fare buckets as the airplane sells out. In AC world, prior to introduction of WS fare buckets, the price difference between Tango and Flex was constant (with a few exceptions).Also AC traditionally maintained inventory in all three fare buckets right up until departure. Therefore the highest Tango bucket was priced higher than discounted latitude fare.

The old AC revenue mgmt approaches made it easy to tell if there was oversold flight; no Tango (on an otherwise route which featured Tango) meant the flight was slightly oversold in economy but seats available in business..... No Flex and Tango meant the flight oversold over all (there were not enough open J seats to cover the oversell in Y). Today there is no such methodology as AC will price match WS and vice versa.