No they arent the same cost.
If able to be booked online (ie only the simplest of routings, not including most partners and excluding some origins/destinations even on QF routes), then
one-way award outbound
+
one-way award inbound (using exact reverse itinerary and no extra/less stopovers)
=
return award
If unable to book online then the assisted award booking fee means 2 one-ways are more expensive than one return.
If able to book online but routing/stopovers differ on inbound/outbound, then return award cost may be the same as 2 one-ways.