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 2.3.8 for Joomla 3.x is available.
Improved appearance of the catalog: product cards are now automatically aligned in height and width. You no longer need to select the width and height of the item card in most cases. Improved product mini-cards template, now it is fully interactive: the user can select the quantity of the item and set the item options directly in the card without opening the product page. The “Add to cart” button is automatically placed down of the card to improve the look of the catalog. Demo.
Fixed calculation of the price and weight of the formula, giving an error in some cases.
Sending an order letter has been improved: now when answering an order letter, the address of the customer or manager will be automatically substituted in the "Reply to" field.
Improved adaptation of price lists to the width of the screens of mobile devices.