I also included KS tiers because they sell at roughly the same prices. I didn't include Pro KS because they sell significantly higher

Buyers are at 12.42 keys so I'm excluding the sales 12 keys and under

No KS:

https://imgur.com/V3NeLzo

Sales:

Past 30 days

1 @ 13 keys, 16.44 ref, 13.35 keys (~13.4 keys)

1 @ 11 keys, 46.11 ref

1 @ 11 keys, 40.00 ref

1 @ 12 keys

Buys:

Past 30 days

1 @ 10 keys, 47.33 ref

1 @ 10 keys, 52.88 ref

1 @ 11 keys, 23.00 ref

1 @ 11 keys, 24.88 ref

1 @ 11 keys, 34.33 ref

Basic KS:

https://imgur.com/FU8zsgQ

Buys:

Past 7 days

1 @ 13 keys, 22.88 ref, 13.48 keys (~13.5 keys)

Specialized KS:

https://imgur.com/7DPey5D

Sales:

Past 7 days

1 @ 13 keys, 7.55 ref, 13.16 keys (~13.2 keys)

Buys:

Past 7 days

1 @ 12 keys, 36.22 ref, 12.76 keys (~12.8 keys)

Going with 12.8-13.5 keys