Filter posts on new page

You can do this with a combination of rewrite endpoints and the pre_get_posts action.

First, your taxonomy has to be registered with some specific rewrite arguments to enable this, particularly, ep_mask:

register_taxonomy(
    'customtax',
    'posttype',
    array(
        'rewrite' => array(
            'slug' => 'custom-tax',
            'hierarchical' => true,
            'ep_mask' => EP_ALL
        ),
        // other args...
    )
);

You can then add an endpoint for your filter, also on the init action:

add_rewrite_endpoint( 'low-price', EP_ALL );

Note that rewrite rules need to be flushed at this point for the new endpoint to exist.

The last step is to then hook pre_get_posts and detect the low-price endpoint, and apply the proper meta arguments to the query:

function wpd_filter_my_tax( $query ) {
    if ( $query->is_tax( 'customtax' )
         && $query->is_main_query()
         && isset( $query->query_vars['low-price'] ) ) {
            $query->set( 'meta_key', 'price' );
            $query->set( 'orderby', 'meta_value_num' );
            $query->set( 'order', 'ASC' );
    }
}
add_action( 'pre_get_posts', 'wpd_filter_my_tax' );