Spears & Munsil High-Definition Benchmark Blu-ray Disc Edition for $25 with SuperSaver shipping at Amazon -- got mine ordered. I don't see any more discs there with the free shipping, but check back later. Amazon can behave strangely sometimes with searches not revealing items that are there or only showing "affiliated vendors."
Back on topic, each disc has its own advantages. At 1/20th the cost of a professional calibrator visit why not own all three?