Just to be clear, do you need to pay the 10 points for each Spider-Bot you have on your force at the beginning of the game towards your force total? Or does the 10 point cost for each Spider-Bot only matter if they are KO'd for scoring purposes?

If you have them on your force at the beginning of the game, you will need to pay their point cost.
If you are bringing them in with Spider-Man's trait you do not need to pay their point cost, but your opponent will score their point value if he KO's them.