The reason that SMS sent in Hebrew seem like they cost more, is you can send less characters per SMS.
Since Hebrew letters need to be "encoded", they count as many more letters.
When a message is sent with any non-English characters the entire message must be sent encoded (even the english ones)!
Therefore each letter (depending which one) can be counted as 2 or even as much as 4!
Added (08/08/23), the program will show the remaining and count Unicode, showing the amount left and will also turn red, when the message includes Unicode.
You can also check which words are unicode by going to https://jlssolutions.com/TestSMSText.php and pasting your text.
