I'll certainly agree there are SOME manufacturers doing precisely what you're stating, but it is not all of them. Spondoolies, for example, sent their first SP30s out in July. If what you say were true, then they'd been mining with those SP30s since May - which simply isn't the case. They never even received the first of the Rockerbox chips until July, at which point they realized the chips were way off of the specs they had simulated (promised 6TH/s got 4.5TH/s with higher power usage). Same with Bitmain's S3. That machine went on sale June 30, so according to you they'd been mining them since April. Initial specs for the machine were 504GH/s, later reduced to 478GH/s. The actual released machine was 440GH/s because of lousy DC/DC converters.
Spodoolies may have a slightly different business model as they also offer hosting. And their rates are not really good. No idea if its just them or electricity costs in Israel are just pretty high.
They offer the hosting as a convenience, and yes I agree they price it extremely high. $500 a month is a tough pill to swallow since there are far cheaper options elsewhere. They don't have the capacity to host a ton of miners. They've come out and said as much on their thread, which is why they initially partnered with the facility in Washington - further supporting my point that not all companies are pre-mining their hardware before sending it off to customers. I'm quite sure that Spondoolies didn't ship a boatload of SP30s to Washington, mine them for months, and then decide to ship them back to Israel to send to customers.
Don't get me wrong, I do indeed believe there are companies doing exactly what you're accusing those companies of doing. I also agree that your average consumer doesn't have a snowball's chance in hell of competing with the guys who are producing the rigs if those guys are also mining with them.