Agree never skimp on the tx/rx, you have INHO the best tx/rx.
ESC, you don't need to spend a fortune but I believe you MUST have one that has a program card. Being able to dial in drag brake and other features is critical for racing competitive. The Hobby-Wing is in reality a cheaper exact version of the more expensive ESCs.
Servos, I prefer a balance between speed and torque, metal gears and ball bearings are a must. There are several mid $$$ servos that can meet these needs. But since $$$ is not a factor I would buy the SAVOX high speed/good torque servo SC-1257TG or SC-1258TG.
Batteries, the batteries run a the recent Reedy Race were ORION 4500/100C for only $65 at A-main Hobbies. So spending $100+ for pack is definitely NOT necessary. Heck I use for local racing, HobbyTown shorty's 4600/90C for $49 and have plenty of power and battery life. Just ensure it is 90C+, I have the ORIONs for bigger races where .01 seconds can make a difference.
Bottom line IMHO here is I believe if you can spend less, but don't go to cheap:
Radio/RX - A must $$$, its not feature but quality and reliability.
ESC - Shop around, needs program options
Servos - shop around, but get a rugged servo
Batteries - shop around, but nothing under 90C