http://www.ebay.com/itm/HONDA-1969-1970-CB750-CB-750-Sandcast-early-rolled-rear-rim-wheel-Sandcast-/121295733613?pt=Motorcycles_Parts_Accessories&hash=item1c3dca036d&vxp=mtrfor what it's worth; my observation and humble opinion........
1. i see no rust on exposed bead face.
2. the rust on the top of the bead does not *appear* deep or extensive enough to compromise safety. (yes, rust is into the steel, but i would suggest not deep enough or extensive enough, to make the rim unusable or to not be able to save the rim.)
3. the rust does not appear deep around spoke holes. as long as there is no rust around the holes, the spokes should be able to be tightened for truing purposes.
4. only 2 rust pin holes are visible in the rim body. of course, there could be others, but the pin holes could be welded closed.
again, in my humble opinion, unless there is rust through the bead or around the spoke holes and the rim body has no extensive thinning or a lot of pin holes and if the rim could be had for $79.95 + $25 shipping, it would be worth the gamble. without rust where i just mentioned in the previous sentence and with proper repair, the structural integrity should be intact. in my humble opinion............ despite all the "if's," still worth the gamble, if rim could be had for $105.
probably some of us have thrown more money away on a bad date and/or drunk.