Avan.market
Instant buy/sell with a genuinely unusual perk: price goes up while you wait, you get paid the higher number.
Avan Market does instant-buy/instant-sell for CS2, Dota 2, and Rust - bot-stocked, not peer-to-peer. Rust's in there properly, just not the biggest catalog on this list.
If the price of your skin moves up while your sale is processing, Avan pays out the higher number instead of the one you were quoted. Most places would just pocket that difference.
Reputation is solid and consistent - complaints, where they exist, are about a slightly dated interface, not anything involving money.
Avan's own deposit fee schedule lists a ruble-denominated rate alongside the usual card/crypto options - a real chunk of CIS users.
Live, computed fresh from our own database - see the full comparison for how every source is measured.