Hi,
The feature is not available yet in HikaMarket but is in our TODO list (it already has been asked in the forum).
But, even if the feature is not fully there (as a built-in option), it is possible to implement it.
The idea is to use the "product approval" so when a vendor will create a product, the product won't be visible.
The "product approval" feature require that an administrator approve the product (changing the "product_type" into "main" instead of the waiting approval one).
Thanks to a custom item field and a custom plugin ; you can have a product that your vendor could buy, the product will have an item custom field with the id of the product they want to approve.
In the plugin, you can add the button in the product edition toolbar ; when the vendor is editing a non-approved product, the button will point to a "add-to-cart" link which will fill the custom item field using the right product id value.
Then, when the vendor will pay and confirm his order, the plugin will see that there is a special approval product and will change the product type of the targeting product.
Instead of the "product approval", you can also use the "publish" state and do not allow the vendor to publish or unpublish their products.
So when the vendor want to publish a product, it will require a payment (with the same kind of process that I explained just before).
I hope that my explanations are clear enough.
Regards,