You are being scammed by them. You should negotiate until the end or walk away. There are many companies like that around that can offer you a cheaper ride. I believe the price should be only 280,000 VND for a boat accommodating two adults and two kids.
@๋ถ์ด์๋ง์๋น _BoongMomDad ะัะป ะฑาฑััะฝ
Oh, all right! I will remember your advice๐ญ Thank you for the good information๐