Looks like Southwest can be had for $300 per person and DL for $312 with a connection at either CVG or MSP. All depends on how much you value cash vs. miles. Miles can go further than cash but you have to do what's right with your financial situation. If you can afford the tickets, it's a better value to purchase them and save the miles for a bigger trip.
For example 60k will get one person roundtrip from the US to Europe and 45k will get one person roundtrip US to Hawaii.