Trisyl azide; why this stuff is so expensive?

From US2006/0069286Al, 2,4,6-Triisoprorylbenzenesulfonyl azide synthesis:-

To a solution of triisopropylbenzenesulfonyl chloride (6.94 g, 22.9 mmol) in acetone (115 mL) at 0° C. was added a solution of NaN3 (1.64 g, 25.2 nnnol) in water (10 mL). The mixture was stirred for 30 min at 0° C. and then was warmed to rt and stirred for 1 h. The mixture was concentrated, diluted with water, and extracted with DCM(3x). The combined organic extracts were dried (Na2S04) and concentrated. The residue was purified by flash chromatography (EtOAclhexanes) to provide 6.71 g (95%) of the desired sulfonyl azide as a white solid. 1 H NMR (400 MHz, CDCI3): 7.22 (s, 2H), 4.05 (sept, 1=6.7, 2H), 2.93 (sept, 1=6.9, lH), 1.29 (d, 1=6.8, 12H), 1.27 (d, 1=6.9, 6H).

As you see, synmthesis is dead easy and starting materials are pretty cheap. So why the final product is commerically so expensive? Is it because of the patent or is it because safty hazard of the azide?