I have that particular cable, though I bought it on ebay. Works great.
Here is the thing about the dreamcast and vga..... some games only support svideo and some games have cut scenes that only run in svideo. So the more expensive adapters often also have a s-vid out. That is what you are paying for essentially. So it might be worth it to you if you are a big fan of dino crisis or some of the afflicted games.