Filter products by price

With pre_get_posts I extend the query with filters.
I’m now trying to make a custom price filter, because i can’t use the original filter

De code i’m using:

$minprice = 0;
$maxprice = 0;
if ( isset( $_GET['min_price'] ) && $_GET['min_price'] > 0 ) $minprice = $_GET['min_price'];
if ( isset( $_GET['max_price'] ) && $_GET['max_price'] > 0 ) $maxprice = $_GET['max_price'];

if ( $minprice > 0 || $maxprice > 0 ) {
	$compare = '=';
	$metavalue = '';
	if ( $minprice > 0 && $maxprice > 0 ) { $compare = 'between'; $metavalue = array( $minprice, $maxprice ); }
	if ( $minprice > 0 && $maxprice <= 0 ) { $compare = '>='; $metavalue = $minprice; }
	if ( $maxprice > 0 && $minprice <= 0 ) { $compare = '<='; $metavalue = $maxprice; }

	$query->set( 'meta_key', 'price' );
	$query->set( 'meta_value', $metavalue );
	$query->set( 'meta_compare', $compare );
}

The problem is that if i fill in 10 for min_price i also get 2 euro products.
I know WP is comparing the values as string.
How can I make it numeric?