Say you have a cover you dont want toss it into the Pool of forever and take a chance at winning a 4 Star cover
2 star covers you could win (i think 2 stars get 250 iso now)
25 iso
50 ISO
100 ISO
250 ISO
500 ISO
1000 ISO
a different 2 star cover .20
a 3 star cover .09
a 4 star cover .005%
might up your own numbers
3 star covers get 500 now
50 ISO
100 ISO
250 iso
500 iso
1000 ISO
2 star cover
3 star cover
4 star cover
so there is a risk you could end up with a worse item but you could get something better