Two simple alternatives for lowest-cost single servings.

First, buy whole bean coffee and grind a single portion at a time, or buy pre-ground coffee. Whole bean is generally fresher.

1. Lowest cost option: use a French press; pre-heat the water in a microwave; awesome results.

2. Second best ootion: buy a stainless steel Keurig-compatible reuseable pod and an inexpensive single-serve Keurig machine; awesome results.

Best coffees I have found:

Whole Paycheck 365 Pacific Rim Medium Dark Roast (whole bean and K-pod)
Allegro Extra Dark French Roast (whole bean and K-pod)
Whole Paycheck Dark Java French Roast (K-pod only)