I highly doubt much of anything will be subsidized. Valve's goal is to get a LOT of people making steam boxes. They don't want to be the only one, they are just spearheading it. This is similar to Nvidia releasing the shield. They're just showing what the concept will be like then letting other people take it further.
You may be right but I doubt long-term substantial success without some kind of subsidized hardware (even if Valve is buying chips straight from Nvidia, AMD, or Intel) and I highly doubt Valve will spearhead something without taking a very, very strong lead. Being private, they have no shareholders to answer to and no doubt have amassed quite a bit of cash over the past 8-9 years. So in other words, I think they can financially handle selling hardware with a small to moderate subsidized price and also subsidize partner hardware.
In one scenario, it is feasible for Valve to subsidize any steam console made by any manufacturer so long as it comes with the Linux-based steam OS and the hardware has slight changes (i.e. slot grooves for system ram and PCIe slot are slightly different than standard PC hardware) so that units cannot be stripped and sold for a profit to be used in non-steam box systems.
Regardless, they need a compelling unit at a compelling price to get decent penetration vs. the consoles.