I don't think a lox bagel is all that luxurious in the context of getting lunch for the family at a bagel store.
Costs so much in Y-m that I would never consider it. Instead I collect all the ingredients (for a Rosh Chodesh meal or the like).
PRICES ARE ESTIMATIONS off the top of my head, but they should be more or less accurate.
Bagel sandwich - 22 shekel (cream cheese), 47 shekel (if there's lox in there somewhere)
Bagels - 6.3 each (when buying 13) at the bagel store, 4 each (at Nechama bakery, genuine bagels but weird shapes/flavors), 3.5 each (at Avichayil, much better but a shlep).
Cream cheese - 18 shekel for about six bagels' worth
Lox - 19 shekel for about six bagels' worth
Tuna - less than 4 shekel/can
Vegetables for the sandwiches for the sake of being fair - about 15 shekel covers enough cucumbers, tomatoes and peppers. Lettuce is either 3.5 shekel, too much time to check or 8 shekel for prechecked (Mir sale).
Total for 13 sandwiches - about 150 shekel. Savings: about 300 shekel.