Not sure if this is much help but I just priced my own shed build up.
4x2 timbers, 18mm ply roof and walls, 16mm shiplap cladding, 100mm rock wool insulation, 50mm kingspan insulation for roof, pent roof with strong shed felt.
2.4m x 4.8m (approx 8ft x 16ft)
£2500 including vat.
EDIT: This...