Share the price with the 5 top designers and let the dev choose.
Is this a good option?
That's a decent option, but still I think the prize amount should be massively reduced.
Let's see...
What about...
2500 QRK for 1st.
1500 QRK for 2nd
750 QRK for 3rd
500 for 4th
250 for 5th