Because Snapchat makes username changes harder than most platforms, 4-letter handles don't churn back onto the market as often — fewer listings, but the ones that do appear tend to represent a deliberate, considered sale rather than a casual name swap.
Not always — but listings tend to be less frequent, since fewer holders change usernames casually, so buyers sometimes pay a premium for immediate availability.
Open the vault, pick a listed username, and DM the contact handle shown on the site to arrange payment — there's no cart/checkout, it's a direct conversation with the seller.
Crypto-only. See the Terms of Service for the full payment and delivery policy, including the sale-finality and 72-hour issue window.