Hi,
In HikaShop Business you can set ACL on prices.
So a customer who is in a specific joomla group will be able to have see different prices than a customer in the public group.
You can make some products "free" for this group of users. So they can buy them for free (and you can configure HikaShop to validate directly a free order and not provide an invoice).
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.