By upper indexes do you mean higher numerically indexs, the slower classes?.
YesNo, say A-D
Fixed it for you.
Oh, and I think the answer to your original question is: The faster classes can cost LOTS of $$$ to be competitive, even for the older stuff.
The price of a new 2015 Drag Pak was $100K-$110K, if you wanted to jump into the deep end of the pool, and I have no idea how far off from being competitive one straight from the dealer's showroom is.