So I guess one "reason not to go for a Caliburn", as you originally asked, is that it costs so much?
i think a better way to look at it is that the cost/benefit ratio is not sufficient to close the deal.
not a matter of means but of value.
he is already drinking from the extreme tt performance well with his current rigs. how much better for how much more money?
evidently not enough....yet.
so then it comes to the issue of 'i gotta have it anyway'.
i've had opportunities to own a Caliburn for less than i'd been offered for my Rockport (although in the interests of full disclosure, not recently). for many different reasons i never went that way. not that i might not be equally or more satisfied with the Caliburn. i just like the Rockport and did not want it to go.