GlobalFastDelivery via eBay offers this 4-Port USB Wall Charger with Four International Adapters in Black or White for $9.99 with free shipping. Outside of the below mentions, that's the lowest total price we could find by $3. It features adapters for the US, UK, EU, and Australia.

Close prices: MidnightBox offers it for $6.95 plus $3.99 for shipping, and HDE via Amazon offers it for $10.95 with free shipping for Prime members.