So it looks like x-caliber equally configured would be $685, and a carbon six has literally ONE barrel in stock... but when using their barrel configurator, would be $790 to get one equally configured. (and I can't tell if that's including the $75 reamer rental on the prefit option. Honestly I didn't think xcalibers were that cheap.
So with proof being found from some vendors at just a bit over $800... I wouldn't call them expensive compared to their competitors. Considering Bartlein, Benchmark, and others will be well over $1050... this means at most, proof is in the middle of the road on price. Anyone calling them expensive, is probably not experienced in the higher end. My calling them cheap was clearly not right either, which makes sense because we deal with the high end, not the low end.
Tell you what proof wins at, almost every single time; availability. If you absolutely need a barrel, and you're short on time... someone somewhere has a proof you can buy. That's an accomplishment in todays world.