You should shoot them an email detailing your needs. Price depends on what you are looking to have done
Their gold and silver services are for serious serious players.
I doubt RPNY is much cheaper (I personally feel their reputation is slightly overrated). But then if you're going to these (P1/RPNY/Bosworth) guys for custom work, you shouldn't really be worried about price.
If you're just looking for racquet matching and/or general customization, you should contact TW. I believe their price is $20 a racquet.