PC Gaming

Again, that doesn't mean they're not competeing. Valve is using their presence in the online retailer market to help fund their hardware, but its not like they're releasing them for free or anything and its not like most other hardware OEMs can't do this. Companies like Asus and MSI aren't small companies, they can and do use the same tactics if the market is worth it. Even assuming they're released literally at-cost, Valve isn't exactly an established OEM - other companies already have decades of experience, established computer manufacturing and logistics networks, Valve is the new disruptior trying to get established, not the other way around.