Hello Folks,
Not only is Silo $109, but it also offers the following:
“A single Silo license allows an individual to use Silo on up to THREE computers,
which can be any COMBINATION of Macs and PCs.”
“Future versions of Silo will be released “simultaneously” on Mac and PC.”
Cool!!!
You don’t see this kind of offer with many applications.
.
Have you tried the demo of Silo on the Mac yet. It’s still got some work, IMO. The interface, and viewports are a lot slower than my PC’s, and the edge-loop, and edge-ring functions still must be keyed twice in order for them to work. Granted it’s only $109, and I bought it about two months ago, for the PC. The Mac version doesn’t seem to be quite as responsive, IMO.
I love Silo, and most of my models on my site start out in Silo, but I will reserve judgment on wether or not it’s a better buy than Modo. Silo lacks a lot of things that I would really like to have. UV mapping, layers, separate multiple combined objects, better instancing, parenting, etc… etc…
Silo is just getting started. Once it’s up, and running on the Mac developing new tools and features will be a breeze for the developer(s). Layers will probably come quickly.
If he sticks just to basic modeling tools only, and does not stray from the modeling aspects of developing this package I think it will be an extremely popular modeling tool. The less he strays the more focused he will be on the modeler.
I think that was one of the original goals of MODO, and is where MODO is right now. Very intuitive, and intelligent looking modeling package. 
I am serious about getting it.
I am getting SILO too though. You just cant beat that price.