Mapping Between Tables

We have a Item table and a Price table. Structure is mentioned below. An Item need to be matched with the Price table (or vice versa is also fine) and get the Cost from the Price table. The challenge (which I feel :) ) is, mapping or Columns to be looked up between these two tables are not fixed.For an Item, Country, City and Number of Days columns can have a value or can be null. For ex, Paper, US, New York <10 days is one combination which should be matched to the Item table. For Paper, UK, NULL, <5 days is another combination which need to be checked. it is kind of dynamic look up of columns between the two tables.

Price Table
Item Country City Number of Days Cost
Paper US New York <10 100
Paper UK <5 150
Paper Chicago >10 200
Pen China <10 250

Item Table
Item Country City Number of Days
Paper US New York 5
Paper UK London 3
Paper US Chicago 15
Pen China Shangai 5
Paper China Beijing 15
Paper US Chicago 5