I recently discovered the TopCashback site after it was mentioned on Ozbargain.
I have only just started to use TopCashback, and I see that in my limited experience it offers greater cashbacks than Cashrewards (I am sure there are exceptions to this rule).
When looking at Ebay, TC offer 3%, while CR offer up to 1%.
From this, would it be reasonable to assume that both companies receive a similar cashback from Ebay, say a total of 4%, with TC keeping 1% and passing on the difference to the customer, and with CR keeping 3% and passing on only 1% to the customer?
Your assumption is correct