Pricing Function

   my $price = 24.74;

   print $ebay->format_price($price,1) # prints '£24.74'
   print $ebay->format_price($price,2) # prints '24.74 GB Pounds Sterling'
   print $ebay->format_price($price,3) # prints '24.74 GBP'
   print $ebay->format_price($price)   # prints '£24.74'