Not quite so simple.
1. Depends where you fly. On our C182 SMA we saved over £10K in fuel alone each London-Cape Town-London trip.
2. Any engine is vulnerable to a serious failure (though I do fully accept that this is less likely to happen with an engine design that hasn't really been changed in 50 years).
3. We flew (much) further, (much) faster, carrying more and saving almost 70% in fuel with our C182 (compared to the original AVGAS burner) - and it completely removed huge amounts of fuel planning (though the smaller strips became more complicated).
Have you flown an SMA powered machine? You should give it a go...
Cheers, Sam.