So I think we can have a reasonable yield by first setting some expectations
For example, how many games do we expect player to play to unlock all tech. and how much games to play to get a fully loaded tier5 squad.
On average(or what I feel when I am playing) each game last for 20 mins. So it is reasonable to say normally people will have 3-5 games/day. consider players spend on average 1-2hours per day on this game.
I think it is reasonable for someone to unlock all tech of a faction if they continue to play a faction for 2 month or 60days (by the 3 games per day standard) without any premium.
And about the equipment. For a tier5 fully loaded fully upgraded with best possible gears of 6-7squads. from 0 silver(lets say this man spend all of his silver on tier4 and early tier5) to fully upgraded with no money wasted the time should be about 10-15days
And decide silver yield and item price accordingly