You can convert from FAA to JAA for about £12,000 ($24,000), it would be very difficult to do it for $15k
The ATPL theory would cost $4000
JAA CPL Conversion $2000
JAA IR Conversion $8000
JAA ME Conversion $1000
Plus living and exam fees $4000
The above are approx prices, but you would probably be looking at spending more, also dont forget the MCC, which would be another $4000
FlightSaftey are a good school, but there are schools in the USA that are a lot cheaper, which would leave you more money to convert when you return home.