If i remember correctly, previous time i reached lv6 and started getting coins in larger ammount it was still inefficient to redeem charm packs or keys on lv6. And i honestly doubt that would change on lv7.

If person making those lists wanted to make more reliable price table, it should possess average number of coins you get by leveling for lvl 1->2, 2->3 etc., since some items (ichiraku) need 850coins, which you get by reaching lv 4 tree. Average ammount of coins you got up to this point is low. If on the other hand you wanted to recruit kakashi (3520pts), you need to reach lv6 and at that point you earned more average coins than before. And on lv6 you start getting even more, and so on. Progress isnt linear, so using the same coin average for every item is wrong. Dont get me wrong, its still helpful since it gives people general idea, but it makes price range too wide and not neccessarily accurate.