It's actually very easy to model accurately. Focus solely on their most mature market - ANZ (refer to Note 2 of their audited accounts). In FY19 ANZ EBITDA (after corporate costs allocation) was $60m and 30 June 19 customer numbers were 2.8m - so EBITDA per customer of ~$21.50. In FY20 ANZ EBITDA was $115m on 3.3m customers - so EBITDA per customer of ~$35 per customer. I am forecasting FY21 ANZ EBITDA of $180m on 3.8m customers - EBITDA of ~$47 per customer.
The US is quite some way behind this currently and is likely to be less profitable per customer initially, but the addressable market is more than 10x ANZ so the scale benefits will eventually be substantial.
These are the sort of outcomes being modelled by the likes of Bell Potter, Morgan Stanley and Credit Suisse to arrive at price targets north of $120.
