I sold my entire collection of Big League magazines (entire sets from 1979 to 2011) which included the Grand Final edition, Season Preview & Review editions to a buyer for $1,500. They were in excellent to Very Good condition and included all posters. Basically I had over 30 team posters for every club, player posed and action shots etc. I was sad to sell them but ran out of storage space to keep them.
I believe the posters add value and price significantly reduces if posters are missing (just see Dan's collectables). Also, if there are pen marks on the team list pages that would also reduce their value as real collectors love a magazine in mint condition. of course Big League went several years (2005 - 2011 from memory) without posters as the editor advised me it was too expensive. However, posters returned in 2012 and that is when my current collection restarted.