My bad on the rounding; it would actually take 162 days if everyone was paying their ichor share every 6th run as opposed to 105 days if they were leeching.
You make it sound like you'd be losing out on millions here. If 5 people were using their ichor instead of 6, everyone would still come out ahead on ichor and the person would be done leeching in 35 runs. You would have paid for an additional (not even) 1.2 runs or in other words you donated less than a mere 7200 ampoules. I'm pretty sure everyone that plays with any sort of friends doesn't mind giving away 7200 ampoules so their friend can have their weapon 57 days faster.
The person leeching could always do something else to chip in like pay for all the lamps, not lot any drops (tatters for everyone else), etc. Hell, you the person could even avoid leeching by buying the ampoule items (very cheaply, might I add) when it's their turn to buy feathers. If you are paying for 30k alexandrite I'm sure you could pay 500k or whatever for your feather items every 6th run. Even rounding Odin v1 to twice a week instead of once every three days and 17.5 weeks is pretty reasonable for anyone to come up with 100k ampoules now.
XI Wiki


