There’s really no way to judge how much a custom plugin will cost without having the details of the needed plugin. If you post a detailed list of what the plugin needs, then you’ll get some offers.
Great. You have to make sure that you always include those.
<?php wp_head();?>in your header.php, and also
<?php wp_footer();?>in your footer.php.
I definitely agree that it’s impractical to have reviewers give details on every single thing that needs work, but one, or perhaps two, would be a huge help.
I have made “lite” versions of some of my plugins, with commercial versions available here. I’ve found that a lot of people will try the free one, and if they like it, will spend the few dollars to upgrade.
So glad to have an item included in the list!