To keep costs down it may sometimes be preferable manufacture certain components of your building using softwood. Beams like roof rafters, which are not always readily visible, may be produced in softwood. However for the main structural beams oak is always used.
The overall cost of your building will depend on the ratio of beams in oak and softwood and you can choose from various options.
A budget outbuilding intended for use with cars or as storage may require a thinner oak frame (with post sizes of 150mm/6”). This combined with softwood intermediate studwork and roof components will offer a lower cost alternative to producing every beam in oak.
An impressive feature building for use as accommodation, entertainment or commercially might require a sturdier oak frame (with post sizes of 200mm/6”). This could include impressive oak roof trusses and beams with a choice of oak intermediate studwork.
Since all Oakmasters buildings and solutions are bespoke rather than mass produced standard kits the pitch of your design and cost choice is entirely up to you.