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.