I looked into 25 purple troops.
putting 10 troops in it, costs 1430 ham.
I upped 1 start troops to tier 6. That is 2x 10 1 stars. This upped 1 star 6 delivers 80 points instead of standard 40.
first costs 50, second 125
first tier goes to 1 4 and delivers 64 points.
2nd tier goes to 1 6 and delivers 80 points.
so… just viewing what costs are for x tiers.
If i put 10x 1 4 that costs 50 k (just to level them to 1 4) + 1430, total 1480 k ham and i get 640 points
If i put 10x 1 6 that costs 50+125 k (level them to 1 6) + 1430, total 1555 k ham and i get 800 points.
If i put 10 x 1 7 that costs 50+125+122 (27 troops total) is 1727 ham total which gives 880 points
if i put 10x level 2 troops thats cost me 1430 and gives 900 points.
So relatively leveling your hopeless 1 star troops 2 x 10 is not this bad…
So 10x 1 4 costs 1480/640 ham per point is 2,3125
So 10x 1 6 costs 1555/800 ham per point is 1.94375
So 10x 17 costs 1727/880 ham per point is 1.9625
so 10 x 2 costs 1430/900 ham per point is 1.58888
It seems like putting them to 1 7 costs more ham relatively. So putting 20 1 stars in a 1 star is not that bad…
Someone who has done these calculations before or wants to add something? I’m curious what happens on lower levels… As i see this now it could be that from tier 29 to 30 it could be same expenses…
Hope to have added something here 
Addition… 800 points will cost 1555 ham with 1 6 troops. At tier 1 they deliver 40 points so will cost 2860 ham to get to 800 points. So though 2 star troops are better, if you’re out of them it’s much cheaper to first bring them up some tiers and upping will be faster.