Some equipment sold in europe has either external or internal voltage switching capabilities. These would not affect the value in the US. However this must be stated in clear language when advertising. Items that do not have this capability are essentially useless in the US unless a transformer is used as previously stated. Pray tell, who would want a transformer in the path?
Buying Audio in EUR and bringing it to the US for resale
I have the opportunity to pick up some high end UK gear ( 5k-10k resale range ) does the fact that it is 220v going to heavily impact selling price back in the states? I wasn't aware of the 50/60 frequency issue, and it seems that people who rave about $3000 cables are the same type that might have a problem with the voltage at a slightly off frequency.