arf, they're probably going to work the same as with cellphones :
Vodacom, for instance, pays on activation of a starter pack, R180 (I believe this changed in recent months though) and they pay a commission PER voucher recharged on that specific ICCID (sim).
The potential recurring income for a company who sold the SIM (with a fancy new phone) would be around 135-250 rand per SIM they sell (working on an average recharge of R450... I work with these figures each month, so I can tell you now its even more than that)
The guy then makes that money FOR LIFE, and is able to discount the cellphone sold (terms and conditions apply : activate sim in store) and is able to sell the cellphone for way less.
One company makes around 230k (and growing) per month RECURRING revenue. So if they stop selling cellphones NOW, they'll be getting that income for a long time to come still.
So if HFC sold 2000 modems, and get paid a measly commission of R50 per connection for the life of that connection, they'll be making a recurring income of R100000 per month for the rest of their life (or until the connection is terminated) So if they work on very small margins, and you factor in HFC is subsidising the modems to get a few thousand out (without strings attached, but really, who the hell will buy a modem specific to iburst and NOT connect to the service...)... they'll still make some nice profit after the 2nd month or so.
Thats a potential 1.2 million rand per year income they can achieve (if I work with the thumbsuck values mentioned)
So this all makes perfectly sense to me....