This achievement is obtained in the game Luftrousers 3.
Purchasing all 10 upgrades in the game costs a total of 2000 coins. You start with 100 and can get 50-150 each wave.
Each wave ends when you destroy every plane and ship. You also need to visit the shop or blow it up. However, if you hover in the sky for a few seconds without any enemies near you, a UFO will fly down. The best way to do this would be to destroy everything and leave the shop unvisited.
This UFO yields 35 coins each time when destroyed, it will then spawn again within a few seconds and you can just grind kills, racking up those coins. It'll take a little while, but it's way less effort and you can just listen to music whilst you do it. I think it's also the second largest source of coins in the game, behind the large ships (40 coins).
You get three lives, but you can tank as much damage as you like as long as your heat gauge doesn't max out. If it fills up, just stop shooting briefly to let it cool down. Hovering too close to the water without the upgrade will also fill it up.