A one time fee seems like a bad idea, and here's why. The labor cost of paying translators is directly proportional to the number of letters of average length received per day, not the number of clients. If you offer free translation services, you're going to have diminishing returns.
Here's the math behind it:
Let M represent the number of men enrolled, N the average number of new men enrolling per year, W the number of women, T the number of translators needed, C the fixed cost of enrolling, and R is the average annual translator salary.
The total revenue taken in annually is NC.
If every man writes only one woman once per day and she responds, then there are 2M letters to translate per day.
Assuming that a translator can do 2 letters per hour, for an 8 hour shift you would need M/8 translators. So that's an annual cost of MR/8. (Let's ignore the fact that M changes for the sake of simplicity.)
HOWEVER, with free "emfs" most guys would communicate with multiple women until they settled on one. So realistically the number of letters would be closer to 8M. The annual translator cost would be MR/2.
So you have NC - MR/2 to cover annual operating expenses. Since C is fixed, N has to grow every year to cover the increased growth from the previous year. Granted, M will decrease some as people get married, drop out, etc. But the revenue stream isn't stable. Granted, there are a LOT of assumptions in this analysis, but I think the logic holds. And yes, I'm a math geek.
(NB: interesting that W never came into play.)
I'm beginning to understand why they charge for emfs. I think there should probably be several tiers of membership pricing levels. At the basic (free?) level, you can browse around, and maybe get a few free translations a month of letters of limited length. At mid-level, you get full scale translation services, no limit on length or number of letters. The best plan gives you webcam access, help with visas, maybe tours, that sort of thing.
One thing I'm not sure about is how (much) to pay the agencies, assuming the head office takes in all the money. If a handful of agencies are doing most of the business, how are funds allocated to reflect that? Maybe a fixed amount with bonuses per 100 translations?