If it is of any help, here are the prices from Craig's poll, converted to USD at the current approximate rate of exchange at the time of writing;
£9.99 (Download), £14.99 (Boxed) = $17.55, $26.34
£14.99 (Download), £19.99 (Boxed) = $26.34, $35.13
£19.99 (Download), £24.99 (Boxed) = $35.13...