rolland, there are quite a few independent designers out there (me included) and a few others on this forum.
the timber framers guild is a wonderful resource as well.
and jon noted quite a few of the issues with timber frame design in general. lots of options, lots of variables, and when you get into open pavilions, you complicate matters with uplift and wind loading, more so that with the basics of roof load and sizing.
your pricing sample doesn't really tell the whole story. stick trusses will blow over just as easily or more so than timber trusses. you haven't really addressed how these will be attached to the ground - sitting on posts / piers? sitting on walls? what holds the walls together? are they sheathed with plywood and siding? with windows and doors?
you can find local mills. try looking on the forestry forum, or contacting a member here named jim rogers. lots of sources for larger than 6x materials. length might be a limiting factor too.
in the end, you need to decide what is more important - money and time, balanced on the use and look of the structure. what is important, and where do you want to spend your money and time....?
