Hi
Try this:
selections back price is equal or less than 3.00
and selections trigger expression match_index is equal to matching_number
matching selections are sorted by back_price by default, so no need to sort the matching selections. The second condition chooses the highest matching index of the matching selections.
another way:
selections back price is equal or less than 3.00
and selections back price is the maximum
please use test mode for trialling.