These are valid points: the NBN need not return a net profit to be a worthwhile endeavour. However, it is extremely expensive, and the Government has claimed that the cost will be offset (at least partially) by significant returns.
It is important that these analyses are done because until they are the real cost of the NBN cannot be ascertained. If the NBN will cover its own costs, it is certainly a worthwhile investment. If it will make a $5 billion loss, it's probably still a worthwhile investment. On the other hand, if none of the costs are to be recovered, there are probably more effective ways of spending $46 billion.