Sites like Newegg, Amazon, or the official Avast store often have 50-70% off deals during Black Friday or Cyber Monday. A 1-year, 3-device plan can cost as little as $20–$30.
Legitimate discounters (like StackSocial, Newegg Flash, or Groupon) sell 1-year Avast Premium keys for as low as . These are OEM keys, but they are legal and safe. 94fbr avast premium security new