Provide me with a $40 virgin mobile top-up and I'll provide you with $30 in BTC at bitstamp rate.
I wish I can but it's not possible to buy those top-ups via phone bill which actually makes sense.
The problem is that phone operators have a 60% fee on premium sms services...
I think there is a way to keep the fees between 20 and 30%, otherwise it wouldn't be profitable for sellers to offer their goods with these kind of payment. Maybe someone has already set up such a premium gateway.