Thats not the case always. OP may have done many smaller transfers and even work with him for a long time and trade more than 26k in total, but when the amount became sufficent enough then other party decided to scam. I am not saying this happened here, but it may have been like this.
I understand what you mean. Even they had hundred of deals before. I would like to tell him, Never go all in until you don't know who is he and you cannot do anything if he does cheat. In this case, Naster did. You will be surprised, even I don't trust Most Trusted exchangers and trading platforms like Binance. I have created a Scam accusation about Binance before. You can check this out
(Scam) Binance Block Users Withdrawals - You could be the next Victim. I never Hodl all my balance in One Wallet. I split them into several wallets. So if a Platform does any kind of cheat like Binance did with a lot of Users. I can still be safe from them. So, Never trust too much with your hard-earned money.