Why Is Big Grin So Expensive?
They are rarely obtained as it is one of the first facemask skins in the game. This rarity is naturally reflected in its price. It is also more liked by the Rust community than other masks in appearance.
How to Get Big Grin in Rust?
If you have a high quality crate in your inventory in Rust, you can try to drop skins by opening it. But it all depends on your luck. If you want, you can buy it for money by registering with one of the third-party Rust skin sites. Otherwise, there is no method that you can get for free.