How about saying after a particular hunting time, one should have >50% chance to get at least one drop?
Assume 15 mins per pod (ofc some ppl can do it faster, but I believe 15 mins is fast enough especially if wc/coffee/cigarette break are taken into account)
If the rate is 1/500, one needs 347 runs to have more than 50% rate getting at least one drop. That's like 87 hours or more than 2 weeks full time hunting.
1-(1-1/500)^347=50.07%
For 1/700, one needs 485 runs, which is 121 Hr or 3 weeks full time hunting.
1-(1-1/700)^485=50.01%
How much time does people need to work for earning 150 USD/dts to buy a STA? Obviously 1/500 or 1/700 is way too low.