198,000 など、3桁ごとにカンマを入れるのがめんどくさかったので、ごくごく簡単に作ってみました。
set thePrice to 198000 as string
set AppleScript's text item delimiters to ""
set thePrice to every character of thePrice
repeat with i from (count of thePrice) - 3 to 1 by -3
set item i of thePrice to (item i of thePrice & ",") as string
end repeat
display dialog (thePrice as string)
ハンドラで使用する場合は
display dialog (makeComma(198000 as string))
on makeComma(thePrice)
set AppleScript's text item delimiters to ""
set thePrice to every character of thePrice
repeat with i from (count of thePrice) - 3 to 1 by -3
set item i of thePrice to (item i of thePrice & ",") as string
end repeat
return thePrice as string
end makeComma
現状では整数のみで小数点には対応していませんが、ひとまず。