The above solution does not mention how much it cost to buy all of the upgrades.
There are five upgrades in the weapon shop.
1. Heavy Gloves: 4,500 pixels
2. Power Ring: 8,000 pixels
3. Midas: 2,500 pixels
4. Magnet Bracelet: 3,000 pixels
5. Cerberus: 6,500 pixels
For a grand total of 24,500 pixels.