Sign EURO looks like well on my polygon (see screenshot attached).
I think you database is not UTF-8 format. Try to change the format of you database and all table columns with type VARCHAR from ascii format to UTF-8 format
This problem is specific to your site. It requires a thorough analysis of your site. The reason may be third party plugins you use on your site. Or may be some issue of the Joomla template used on your site. I think it is not the issue of the component IPrice calculator LIGHT. You are the first who faces such a problem.
New version of IPrice minimart 2.4.2 for Joomla 4.x.
Added "Do not use cart" option. In this mode, you can select the necessary products on the page and immediately submit the order by filling out the contact information. The shopping cart is not used in this case. This mode is suitable for organizing a quick order of a small number of goods or for costing and ordering services. Demo price list without using a shopping cart. Demo of a catalog without using a shopping cart.