drugstore.com offers the Green Mountain French Roast Coffee K-Cup 24-Pack (pictured), and the Celestial Seasonings Green Tea K-Cup 24-Pack for $15.99 each. Tick the special offers box and add two packs (48 K-Cups total) to your cart to see the price drop to $21.59. With free shipping, that's $0.45 per K-Cup and $8 under the lowest total price we could find for 50 K-Cups sold elsewhere. For further comparison, we saw 36 K-Cups for $13 a month ago. These fit all Keurig brewers.

Update: Take an extra 20% off via this link. That drops the price of the items above to $19.19 with free shipping.