How much would it cost to replace the IC chip for an Iphone 4s?

Apple does not service or repair the iPhone 4s, they replace the entire iPhone for $199 in the US.

Now how would you know you just need that replaced o_O

I hope that device wasn't opened or touched by an unauthroized apple service provider; because if so you may have voided the warrenty of the device; or it being replaced

Take the iPhone to an Apple store genius bar and have them check it...if you still have AppleCare coverage it may be something they can replace the iPhone for free under that extended warranty. If not, they will let you know more about your options and costs.

If you cannot get to an Apple store, you can try service through the appropriate country support number found in http://support.apple.com/kb/HE57 or try the ExpressLane at https://expresslane.apple.com to open a service request ticket.

nebsgogone wrote:

Took it to a repair shop and they said it is too small for them to replace.

If they opened the phone, Apple won't touch it any more. You've forfeited the right to have it serviced by Apple. If the shop you took it to says they can't fix it, buy a new phone.