Testnet is not for sell. People must mine Bitcoin Testnet tBTC but it is for developers to test their codes, products before deploying it on Bitcoin mainnet.

Selling Bitcoin Testnet is scam.

Testnet Bitcoin. Activate, experience it, but don't trade and get scammed.

Testnet faucets
https://bitcoinfaucet.uo1.net/
https://kuttler.eu/en/bitcoin/btc/faucet/
https://coinfaucet.eu/en/btc-testnet/
https://tbtc.bitaps.com/