At my local Costco, I see a Kirkland brand 100% merino wool quarter-zip sweater being sold for $25. On EMS, I see a SmartWool 100% merino wool half-zip sweater costing $140. Would I be potentially putting myself more at risk if I wore the Kirkland sweater as a layer?
As with everything -- it depends.
My wool socks from wal-mart have outlasted literally everything else we have purchased, including most of our gear. They still keep my toes toasty warm. Wal-mart is a go-to kind of store for hunters in the south because they have good inexpensive warm clothes. Wool socks from wal-mart generally last me around ten years/pair...
However, walk two aisles over, or even in the same aisle, and you will find things that will fail in ten days.
The question could more generally be stated as "does price guarantee quality", and the answer is no. While the stuff two aisles over at wal-mart might fail, the same is true of most other stores. For instance we never buy several of the "Name" hiking brands because they have failed us and rapidly at that (I leave out names because I don't want to smear a brand).
Whether or not you will be more "at risk" depends solely on following one rule. NEVER test new gear at the extremes, no matter how cool, or what you paid for it. Test where failure is not fatal. And that goes just as equally for "name" as for "generic"
On the short run, the answer is no. You will not put yourself at more risk wearing a cheaper product.
On the long run, the answer is not so clear. There must be a reason behind a cheap price:
It is very hard to answer those questions precisely. One thing is sure that on the long run, your sweater will endure more stress. It might fail or succeed.
I was curious to do the same comparison in a store that I trust and who is known to be a fair trade store. The merino sweaters were sold between $50 and $100 depending on the model.
If I compare with your two items, I would probably say that you selected two extremes.
I will probably choose to buy an item whose price will fall between the two for a normal usage. For an extended usage, I will go for the topnotch which is not always the most expensive but rarely the cheapest.
Smart Wool main claim to fame is that their treated wool doesn't itch as bad or shrink as much in washing machines. Otherwise, its all the same stuff as far as its insulating capabilities go.