Quadrivalent vaccine is $20 cash or free with most insurances and covers 2017-18 strains:
A/Michigan/45/2015 (H1N1)pdm09-like virus;
A/Hong Kong/4801/2014 (H3N2)-like virus;
This is the cheapest I have seen for a QIV and takes about 5 min.
Depending on the location, you may not need a membership. Please call your local Costco to find out.
PS This is NOT a political or a scientific thread. If you do not like the deal for whatever reason, do not troll and just move on.