I saw a 360 which had done a gear up landing on asphalt or concrete while I was at Aircrafters in Watsonville.  They were about to start repairing it.  This would have been in 2001.  I was pleasantly surprised at how little airframe damage there was.  The belly pan was ground down somewhat, but the wing spars are about an inch above the belly pan so they were untouched.  Of course the lower cowling needed some local work but the cowling was largely intact.

Of course, the major expense is the engine teardown and the prop (isn't that what insurance is for?) but as far as airframe damage and occupant safety, well, I wouldn't have a major concern about landing gear up in a 360.

That doesn't mean I want to do it.  It just means that I'll be pretty calm about my personal safety it I ever have to do it.  Much less dangerous than landing with one gear retracted.

- Rob Wolf