Let see the math.

One Rigs 6x AMD RX 570 give you 35Mh with Lyra2Rav2 algo.
Net hash rate is: 82Gh, similar 82000/35 = 2480 Rig.
- Blocktime 1 minute.
- Reward is 10 STRAKS.
- 1 day = 1440 min.
So all STRAKS net make 1440x10=14400 STRAKS.

Mean 14400/2480=5.8 STRAK. Similar 5.8 x 4 (SIGT)=23.2 sigt.

Sigt price is 0.0000015=> 23.2 x 0.0000015 =0.0000348.

Result 1 rig 6x AMD 570 get profit = 0.0000348 or 0.0000348 x 8400=0.29$/day
It very cheap for SIGT or Very waste your electrics for you if you mine STRAKS.