I think if you look at the available shed size you need, and price timber up you'll not find too much saving. But that's because people look at cheapest price shed the realise price of timber. But don't realise their build is normally using bigger stronger and thicker timber, if you look at a quality shed with similar materials you'll find you can save a few hundred pounds.
When I built my 8x8 extension onto my 16x8 loglap shed, it ran me to £750 for wood, felt etc. earlier this year.
Sounds a lot, but a comparative shed including insulation, 3/4 plý lined walls and floor, loglap facia was around £1,200.