I think it's a little rude... If you didn't like the style that's fair enough it's not you, guys don't always get it right...
But your saying the stone is too small and you know how much he paid, he just got a new car... That I think is horrible... A car can get you from A-B it is something you need in life.. An Engagment ring is a privilege, he gave this too you because he loves you and wants to marry you, wants to spend forever with you! Size of the rock shouldn't matter it's the love and feelings behind it, what it symbolises...
Everyone is entitled to their own opinions and point of view... But if my fiancé proposed with a fake ring I would still say yes because it's what that ring symbolises not the price tag on it... Having an expensive ring may be great, but knowing that money is spent on a ring when it could go toward a house, or a new car or the wedding itself... I know how much my fiancé spent and I love him for it but when I found out I could have hit him.. I wish he spent less but I love him just the same as should you...
I hope you get a ring that is better suited too you... Xx