If you are looking for fabric suitable to use for a kilt. That is - worsted wool woven in a twill pattern, with a kilt selvedge, following the thread count of registered Tartans, in a good kilt weight - your really only looking at a hand-full of weaving companies.

Of these, Lochcarron is probably the largest. (As was mentioned, Burnett's & Struth, a forum advertiser, is Lochcarron Canada) They have 1500+ Tartans in 10oz, 450+ in 13oz and 750+ in 16oz in their stock list. Stock means that they weave it all the time and will usually have some sitting on a shelf somewhere.

Some of the other, better known names, are Marton Mills in Leeds, Strathmore, House of Edgar, N. Batley, and D.C. Dalgliesh (owned by ScotWeb). There is also Fraser & Kirkbright in Vancouver, BC and about 6 smaller weavers with one or two looms.

We all buy from the same few weavers. Our wholesale prices are all the same.

So the only difference is the retail markup we all charge. The retail markup is how we pay to keep the lights on and the doors open. Obviously an internet-only business run out of a garage, or small storage unit somewhere, will have less overhead than those of us with brick and mortar shops. But the smaller the operation, the less capital and space, so the less selection of in-stock fabrics at any one time. (heck, I usually only have 50 or 60 Tartans in four weights and a couple thousand yards of solid color fabrics on hand at any one time.)

Buying from any of the Mills will give you a quality fabric. The price will usually be only a dollar or two per yard difference.

When you count that the cost of your fabric is only half, or less, of the cost of a kilt, the one or two dollar difference is really small potatoes. Even the difference between 13oz and 16oz is only about 40-50 dollars per kilt.

My advice is go with the best quality fabric you can afford from the best weaver you can find. Buy direct from the weaver if you can. (almost all of them sell retail)
Barring buying direct, contact almost any kiltmaker and they can order fabric for you.

I'm not trying to tell you not to buy from the place you found. If you like them, go for it. I'm just trying to give you some facts so you can make an informed decision.