Great Kilts, as we know them, are merely a stretch of fabric with no tailoring. For that reason, they're MUCH less expensive.

As for weight, that's entirely up to what you're looking to "warm-up". The Great Kilt covers the shoulders, whereas the Little Kilt will concentrate on the... um... lower body.

I'm currently designing and finishing a "tailored" breacon feileadh mor. It will be a hybrid of a breacon feileadh mor and a breacon feileadh beg. I guess that makes it a feileadh-middle? The design is DONE, and is as easy to put-on as a casual kilt. This all came about because the SCA was looking for something that was not available out there. There were also a number of guys that were looking for the "full" look without the pain of the gathering. This will make it as easy as a feileadh beg.

With that, it will be as warm as a "little kilt" with the extension of the "great kilt". Depending on the fabric sources (which are near completion) the cost will put them in the casual kilt range... in wool or other.

This will be an "original" design that will in no way replace the little kilt. It's more of a challenge-and-solution to bringing the breacon feileadh mor into the modern fold. Celtic bands, pipe bands, re-enactors, SCA and individuals are already lined-up! I'll let you know more in 3 months.