Front-end update_post_meta snippet displays white screen?

Change your nonce verify to actually verify and update post meta, else do nothing. But don’t use exit at the top of your template.

// top of page
if ( isset( $_POST['drw_inventory'] ) && wp_verify_nonce($_POST['drw_inventory'],'update_drw_postmeta') )
    { //if nonce check succeeds.
        global $post;
        $postid = $post->ID;
        $data = $_POST['priceone'];
        update_post_meta($postid,'metakey',$data);
    }

// in single.php
$priceone = get_post_meta($post->ID, 'priceone', true);
<form method="post" action="">
   <?php wp_nonce_field('update_drw_postmeta','drw_inventory'); ?>
   <label>This is label</label>
   <input type="text" name="priceone" value="<?php echo $priceone ?>" />
   <input type="submit" value="save" />
</form>