Here are the screendumps from my J2Store / Jevents installation, with the content in Jevents Extrainfo field:
Backend tag {j2store}10|price{/j2store}
Frontend detail view tag {j2store}10|price{/j2store}
Frontend list view tag {j2store}10|price{/j2store}
Backend tag {j2store}10|cart{/j2store}
Frontend detail vew tag {j2store}10|cart{/j2store}
Frontend list view tag {j2store}10|cart{/j2store}