Short verdict
Buy in Korea. Best purchased during a Korea trip, usually because of local access, price, testing, or limited bundles.
Sheet masks are compact individually but heavy in bulk. The best number is the amount you will actually use or gift soon.
What to know
Buy in Korea when promotions are strong and you can check ingredients across brands.
What to avoid
Skip huge hauls if your skin is sensitive, if expiry dates are short, or if the masks are easy to buy online later.
Final verdict: buy a small curated stack, not a wall display.