That makes more sense now that it's explained, Jay. I was thinking more in terms of how people approach me with that eternal question, "What does one of these cost a square foot?".
Usually it's the first or second question they ask when they first meet me at a job-site. I agree that once one nails down what "these" means it's easy to figure out a pricing matrix. I guess that what bothers me about talk of sq. ft. pricing, is not in regards to pricing specifics as you mentioned, but when it is applied as a catch-all concept without specifics.
For example, there is no such thing as a "typical sq ft price for a timber frame" but it IS possible to say " a timber framed New World Dutch barn would typically be x$'s a sq. ft."
I agree wholeheartedly about open ended T and M work. Once in a while I'll do time and material, but with a "not to exceed" number as a cap. 95% of what I do is all solid pricing. I must say that I have learned the hard way what to charge, by under bidding projects. But if I didn't know how much to charge, then I obviously wasn't worth paying that much anyway . That is how one builds a body of work though. I have run across instances a couple times now where people have gone with me because I gave them a firm price. And they were really really impressed that I gave them a firm price! In one case it was probably the simplest house you can imagine, 28'x 32' posts, plates,common rafters, typical bracing. The other timber framer wouldn't give a firm price, said the project was so complicated that there was no way to figure it out and there was no way to figure how long it might take. They also wanted to go sans knee bracing and rely on the stairs to brace the building. And, if the project got to the point that it was too expensive they could always eliminate the timber rafters! I was pretty flabbergasted by that level of unprofessional conduct. This timber framer also gives classes as well! You can't even make this stuff up!