If you were to bruteforce a single MD5 hash, it would take x time to go through all combinations up to 8 characters.
If you were to bruteforce two MD5 hashes, it would still take x time to go through all combinations up to 8 characters.
If two+ hashes/whatever? needs to be cracked, do them at once and it will take half as long.
I guess you can get where I am going with this. Pay more if you want it done instantly, or less if you want to wait for another of the same type