It’s more of a “we want to make sure that this user we’re inviting would be a good member i.e. good ratio/not selling invites”

The current transaction costs for monero are 0.000006XMR, which translates to about $0.001 per transaction.

The costs you have to look out for are the buy and withdrawal fees of the crypto exchange you’re using. If you’re in the EU you should also know a lot of platforms do not allow trading to/from XMR.

Not affiliated with them, but MEXC works in the EU and has a 0 fee XMR withdrawal.

The gold standard for anonymous payments is still crypto for now, monero can’t be tracked in any way. Besides, it has really low transaction costs.