Chelsea are very important to the companies who wish for their club to be noticed. Being Adidas's 2nd highest shirt seller, Adidas has to put out the big money to keep their prestigous partner. Recently spending £300 million on a contract for Chelsea shirt producing, its clear that they will do anything for this club.
Chelsea currently sell around 910,000 shirts a year. Despite not being close to Real Madrid's 1,400,000 they still make enough to match the giants like Bayern Munich.
Chelsea 2012-2013 kit (Home)
Chelsea 2013-2014 kit (Away)