I hear this is the best cycling clothing material. But pricey.
Anyone have a favorite place to buy with good prices?

Keep an eye on : hucknroll.com, backcountry.com, sierratradingpost.com and departmentofgoods.com. Good stuff at really great prices come and go.

Goodwill for non cycling specific wool base layers.

My experience has taught me that nothing is better than merino wool, but indeed it's hard to find the good stuff cheap. But the good stuff is worth it.

So it's a long term effort, I buy off season as much as possible as there will always be another winter or summer to ride in. A lot of the manufacturers sell closeout off season right from their site, the discount online retailers mentioned above are good too. I've got a good collection now, but it has taken me a few years to build it up and I'm always ready to jump on a deal if I see it.

Yep. This and Salvation Army, if you've got one around. I picked up a couple Merino wool sweaters for $2.50 a piece. They're lighter weight than my Mission Workshop Bosun Merino jacket, so I've got more versatility in mixing and matching layers.

Yes if you wear a Large or XL size its going to be pretty easy to fine some good wool stuff at the thrift stores. Anything smaller than that it gets harder, but I have found a couple things over the last year or so.

Merino is great. Sierra trading post occasionally has decent prices for some items. I've gotten a few reasonable wool sweaters from thrift shops.