Yeah, that certainly is the most expensive outer coating I can imagine (bar gold). I don't mean to insight a war of monolithic vs. fiberglass here. I think this is something worth discussing.
The fire hazard is lower than it is for a conventional home. The fiberglass is not batting and therefore not saturated with air to serve as oxidant. Also, the fiberglass is only a thin layer beneath which is polyurethane. To put this in perspective, growing up in Texas, tornadoes are a real concern. I have survived two near misses (i.e. tornado passing within 1/4 mile) but I have never been in a house that caught on fire. There can be no argument that if a fire occurred that the monolithic would have greater survivability than a fiberglass. As far as fire insurance goes, premiums are based on home replacement. In other words on the cost of the home. For a 2900 sq. ft. home that cost $232,000 (monolithic- $80/sq. ft) the insurance will be comparable to the same home that cost only $150,800 (fiberglass- $52/sq. ft).
What I would be most interested in is water and tornado resistance. I have read of past problems with the monolithic dome where the polyurethane became saturated with condensed water vapors associated with the vapor drive created by the hot exterior surface. The vinyl covering while thick is not impenetrable and small puncture marks require repair. Also, concrete is porous and allows water vapor to penetrate. Finally, sealing the base of any dome to the foundation is a vital step. Because of porosity, the monolithic dome can develop seepage problems. On the other hand, fiberglass is not porous and so should suffer less problems associated with both vapor drive and seepage. The manufacturer of the fiberglass dome boasts an 8000 psi puncture resistance. This equates to more than three times the force delivered by a 15 lb 2 X 4 travelling at 100 mph (the Texas Tech tests for tornado survivability). The question then becomes can a tornado lift the lightweight fiberglass shell, even though anchored to the foundation. I know the answer to this one when it comes to the monolithic.