The wool shirts that I've seen on Ron's website look to be of excellent quality and very reasonably priced for new wool garments.
It is definitely worthwhile to keep an eye on thrift shops. I've seen some of the high dollar 'wool' garments sold at the local outdoor megastore (that starts with 'C') and have found that most are actually wool blends with barely 50% wool. I have found much better made 100% wool shirts, sweaters and pants of various thicknesses in excellent condition at the local thrift shop / goodwill stores.
I've bought about 4 100% cashmere shirts (and several 100% merino sweaters) All for less than $10 each. For me, the material of the garment is far more important than the camo pattern - it is very easy to dye a camo pattern into the wool. A couple of the sweaters already have a pattern that camoflauges as well, if not better than any commercial camo pattern. For shirts and sweaters, make sure they fit loosely enough so you can wear several fairly thin layers (each subsequent layer can be a bith thicker) without any restriction of movement. This will also help trap air between layers.
For pants, I prefer one layer of thin (microlight) merino long johns and one pair of wool pants over top. The thickness of the outer pants I select will depend on the temperature range I'll be in, but the long johns will always be very light weight. I have a few pairs of wool pants that range in thickness from superthin (for hot summer weather) to thick military surplus ones for the -40ish late season conditions.
For my base layers, I will buy new. Base layers should always be thin. The best value for the money I've found is the microlight merino wool garments from MEC;
boxers long johns T- shirt