dizzynewheights tbh it sounds like complete horseshit to me. I'm no expert, obvs, but don't these deals usually involve the manufacturer paying the club a lump sum then some agreement being struck on profit share for shirts sold directly by the club
Why on earth would a club pay to get their stock earlier If there was any evidence that this increased sales (and I can't imagine there is any) then it raises the question why your Lutons, your Cambridges, your Coventrys all seem quite happy to cover this surcharge when I don't imagine they're selling any more shirts than we are
I've been told it's to do with staggering the manufacturing - if every club wants their shirt at a particular time, then the shirt manufacturers have a capacity problem. So basically by delaying a bit we're getting off-peak prices (whatever way that works).
Quite possibly your Luton's etc go off-peak in a different way - they finalise the shirt design earlier than most, so that they are actually being manufactured during the previous season.
This may all be hogwash of course, but it does make a kind of sense.