I guess yes, it's all about $$$. You pay for the exam and the prometric center let you take the exam and register your result...but Sun Microsystem will not issue the formal certificate if you dont have SCJP.
But the link given by you does not say that you can not appeear for it.It only tells the path to take the exams . Please let me know if I am not correct,as I have limited money and confident that I can clear SCWCD without clearing the SCJP. That is why I want to go directly for SCWCD .
The product description for the SCWCD exam on the sun website says "Prior to beginning the Sun Certified Web Component Developer program, you MUST be a Sun Certified Programmer for the Java platform (any edition). "