You can add real money to your internal balance and use this balance in your trades! You can use this feature if You do not have enough items for trade the item you want!
If you add money to your account you will get a 20% bonus to your account balance!
But that's not all! If you transfer more than $20 you will get an insane 25% bonus!
Additional 5% bonus if you top-up with a Crypto currencies!