Expect to pay between $200 and $350 USD for a used unit in good condition with all leads and the charger. A "new old stock" (unopened box) 2021 model may command over $400 due to its rarity.
The 2021 iteration of the AACT 395 brought several upgrades over previous versions. Here are the standout features that make it a must-have: aact 395 portable activator 2021
Check that your specific edition of Windows or Office is compatible with version 3.9.5 or later. Expect to pay between $200 and $350 USD