I don't know what prices you pay for E85 over east, but here in Perth, today's metro averages as follows:
Product Metro Average
ULP 129.6
PULP 142.9
98 RON 149.5
E85 184.8
Bearing in mind that Monday is the cheapest day here in the fuel cycle and everything kicks up to its highest price on Tuesday and starts a gradual decline to the next Monday.
Nonetheless, E85 is by far the most expensive option which is not widely available (only sold by 9 sites in the state, with two of those being regional). Given the motor uses more of it, the costs don't stack up.
BTW, no E10 sold in WA.