The total discount of a pair of shoes is $200 x 30/100 = $<<200*30/100=60>>60.
He spent $200 - $60 = $<<200-60=140>>140 for a pair of shoes.
The total cost of two shirts is $80 x 2 = $<<80*2=160>>160.
The initial cost of his purchase is $140 + $160 = $<<140+160=300>>300.
He got an additional $300 x 5/100 = $<<300*5/100=15>>15 discount upon checkout.
Therefore, Erwan spent $300 - 15 = $<<300-15=285>>285 after all the discounts.
#### 285