Hi,
Well, we can't do much about this. However, please look from the perspective of the developer:
They have developed a plugin. It took them a lot of time. The cost for such a development is between several hundred euros to several thousand euros. On top of this, they need to maintain it going forward, supporting newer versions of PHP, Joomla, HikaShop.
The price they charge for the purchase of the plugin counts on the fact that many users will purchase it to recoup the costs over time.
You're asking them for a substantial modification of the code to them. They will have to spend time working on it. So, they have to charge you for that time. That's why the amount is big compared to the purchase of the plugin as the time spent on the modification can't be recouped over time on many users.
Regarding Stripe, I already replied to you in a previous message 2 weeks ago :
Regarding Stripe, the Stripe Connect payment plugin developed by Obsidev and available on our marketplace doesn't send the details of the order to Stripe. I'm not familiar with the Stripe APIs used by the plugin so I'm not even sure if that's possible with them.
Sending the details of the order for this plugin would require a big development, maybe the development of a completely new plugin to support other APIs (like Stripe Checkout).
www.hikashop.com/forum/payment-methods/9...-and-tax.html#366485
In short, it's not possible doing what you want with the Stripe plugin, and developing a new plugin to support this would cost a lot more than the cost of modifying the Square payment plugin.