So as you see the 0.25% fee is not so big deal in compared with another's. As I told before it is quite low percentage in the market (0.25%) and it is beneficial for us I think.
Regarding with frauding vendors, I think you are not right again

let me explain this also. First of all in the crypterion script as you can see there is escrow system and once buyer and seller doesnt confirm the payment the amount is freezed in the website. This is because there is not many wallets. There is actually one wallet (admin wallet) and the rest of all are only shared wallets. So the full control is in admin (website owner). How your vendor will fraud you think ? impossible to fraud in this case. if your seller did not get payment fully then moderator enters and solves the issue. Another point is yes you can freeze the wallet , I mean you can edit the balance of any user from Datebase just in any case.