I'm guessing there is no definite answer for the question I'm asking, you generally price the website dependent on the client needs and taking into account the problems you stated above with bugs etc?
Exactly. Every client's needs are different. Some might need extensive graphics work. Some might need a lot of JS. Others may want a responsive design with elements from the previous two scenarios. Short of going the "I have 5-10 templates that fit most needs" route, you're going to have to build a fair amount from scratch. A hard price cap will inevitably cut into your margins at that point.
So, if you want to market yourself as a discount developer that can provide quality while undercutting the competition, go for it! That's exactly what you should be doing at this point in your development. But pricing should be determined after conferring with your client. A hard cap is just too limiting for all involved. Go to the full post