Or another way to look at it is processing payments costs money. Its a billion dollar industry and a real cost of doing business. Optus provide a free option.
NB Optus charge either a paper fee or a payment fee, not both. So your costs (for not taking up the free option) are capped at $24 a year.
Also payment methods via credit card etc are much less (about 40c a month). If you prefer using BPay (its not 'free' as the biller pays BPay on your behalf) then the option is available but it will cost you $2.20 a month for the luxury.