You may try including the to information in the header and passing that to the mail function instead of explicitly defining the $to variable... Your mail server maybe rejecting the email since the $to variable may not have passed properly, and since you didn't define a from, you'd have no way of getting that bounce back...
$headers = "MIME-Version: 1.0\\r\\n" .
"Content-type: text/html; charset=WINDOWS-1255\\r\\n" .
"To: <gr3gg0r@gmail.com>\\r\\n" .
"From: <gr3gg0r@gmail.com>\\r\\n";
$subject = 'Price Calculator Data';
$message = "Percent= " . $percent . "\nPaypal= " . $pp . "\nSellerPaid= " . $SellerPaid;
mail(null, $subject, $message, $headers);