Here is the prize breakdown for 4th - 12th
2 gem slingbows, 10 raw gleam of each color, 20 lava and 20 water buckets, 20 refined red and pink gleam, 3 steam keys each accept for 4th place which gets 4 steam keys.
The reason for the even distribution past 3rd place was more about rewarding players simply for participating in the contest. The devs were very happy to see so many willing players that were excited about the new chisels that they wanted to help supply prizes but also wished that everybody received some. I hope I explained this right.