Show price info in post preview

Hi together,

how can I display the price information of my added products to a post in the post preview in my blog? I tryed it with something like this in my theme files:

<?php echo get_post_meta($post_id, '_cegg_data_'. $module_id, true); ?> 

But I can’t see info about the amazon product in the linked post.

I hope someone can help me out ??

Thanks a lot!