The special issues of BRW interrupt the weekly display and promotion of the title and I suspect this impacts the sales of the regular issues.
Each special issue comes with plenty more point of sale material than the regular issue and this pulls consumer focus as the photo from my shop shows.
The special issues also stay on the shelf longer and this can make regulars blind to the masthead.
I had a customer yesterday ask me which issue they should buy – they had been sent in by a friend to buy BRW without instruction on which issue. Buy both was my answer.