YQ surcharges are just another element an airline can choose to muck with to bump up or down the ticket price. As an end user I wouldn't bother reading anything

YQ surcharges are just another element an airline can choose to muck with to bump up or down the ticket price. As an end user I wouldn't bother reading anything into it - the total price is the total price regardless of how the airline choose to break it out. The interesting part from the carrier point of view relates to how an airline prorates out the total amount collected in codeshare or interline agreements, and whether corporate discounted fares offered apply to the YQ portion or not (hint they usually don't) and whether all governments have caught up in taxing these in the same manner as a regular fares. I would think of it as a construct for creative accounting more than anything else.