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>