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Have you ever wondered how much a bag should cost? Well, take the total cost of the gear you plan to put inside and get 10% of that. The formula works for most (read: not all!) cases: my Crumpler Whickey and Cox costs close to P10,000.00 and holds about P100,000 worth of gadgets including my MacBook and camera. A hefty bag price should only mean that your gear fits comfortably inside, likewise both your hands are still free.
In the case of laptop sleeves, a good sleeve should not cost you more than P2,000.00 or $40.00. In fact, one of the best laptop sleeves ever invented retails for only P1,500.00: this is the Zero Shock Laptop Sleeve. You can literally drop a bowling ball on top of the memory foam and your notebook will still function afterwards. *