Delta, Air France and KLM all offer open jaw routings; much of my European travel involves arriving at one airport, and leaving from another airport in another country hundreds of miles away, which you can get for normal round-trip pricing, both in money and in SkyMiles.

My most recent European adventure was IAD-CDG-EDI, returning ZRH-CDG-IAD, which I got on AF for 100,000 miles plus $157 in taxes/fees.

Just use the multi-city function on delta.com to look up the itinerary you want.