Telstra and "Cheap" don't exactly go together, unfortunately.
I've sold phones for nearly a decade now and honestly don't believe in "one phone to rule them all".
Iphone 7's seem pretty decent, but as always, sept/oct = new iphone.
Add $15 if you want "Stay Connected" which is Telstra protection package for the phone (Replacement phone if anything happens to yours).
https://www.telstra.com.au/mobile-phones/mobiles-on-a-plan/iphone/iphone-7 https://www.telstra.com.au/mobile-phones/mobiles-on-a-plan/iphone/iphone-7-plus
These are the current prices, Other thing to look into would be purchasing the phones Outright, and signing up on a BYO Phone plan.
https://www.telstra.com.au/mobile-phones/plans-and-rates#byo
The benefit of this is that it's much cheaper per month and if something bad were to happen to either phone, you can still upgrade it to a Mobile Phone Plan and get a new phone. The downside is paying upfront for a phone.
That's about all the information I can give you, the rest is you making a decision, and hopefully coming to see me so I can earn that $$