I bought a 100% merino wool sweater from Costco for 19.99USD like many others here. I don't wear it directly next to my skin, but over a synthetic or silk baselayer. I used the same sweater since it started getting cold in November and have not washed it yet. I liked it so much I bought another; same style and same color. I wore the new one once or twice.

Now I can't tell a difference between them - I can no longer tell which one I've only work two or three times and which one I've been wearing all winter without washing.