Be thankful it wasn't Parcelforce, they charge £12
I don't think I've dealt with DPD but I've had a few things sent via UPS and Parcelforce, pretty straightforward and they've paid the VAT and and import duty on your behalf. The fee doesn't seem unreasonable, though if it was a low value item it can seem disproportionate. You always have the option to reject it, though what happens then is between you and the seller.