Here you go:
According to documentation of get_post_meta , It will return a single value if the third parameter is true. It should be false to return an array.
<?php
$price = get_post_meta(get_the_ID(),'si-price');
foreach ($price as $element) {
if (is_numeric($element)) {
echo '$' . $element;
} else {
echo $element;
}
}
?>