Sure ad’s reviews, guest blog posts etc. (and I’n not thinking of on envato but places like FB, Google plus, etc.) A bit like ‘buy one get one free’ - write a review then somebody writes a review for you - you don’t write review nobody reviews your products.
To me it should all be about links in to get hits and getting known to a wider audience the more followers etc the more chance we have. OK I’m not saying it will generate 100’s sales - I doubt that, but it’s about giving us a ‘chance’ to get sales and if we have say 10 people that means we each have a ‘marketing department’ of 10 people 
that could be worth a few $ in ‘hidden’ costs that we don’t have to pay for. Example if we each spent 1 hour a week ‘co-operating’ on marketing than that is 10 hours - and that is about 9.9 hours more than I currently have but seriously 10 people doing 5, 10 or 15 mins a day can/could create a lot ‘marketing’ and prop. more marketing than we are each doing individually.