The vibe you gave off with this thread was basically "who would be stupid enough to buy one of these racks?" That's why people reply the way they do. If someone implied that a decision you made was stupid, you'd probably be a little upset with that person too. Now, not only have you insulted their decision to purchase a rack, you are calling them pathetic for defending their decision.
I just went through and skimmed this thread again. Really, the only rude remarks I saw were from you, so I don't think this board or the people on it are the problem here.
Do ARS and FB mark up their racks? Of course they do. They are in the business to make a profit. That means charging more for their product than it takes to make it. There is absolutely nothing wrong with that. Are they over charging? Not likely. If they were, someone would step in and bring a cheaper alternative to market. If you think you could do this as good for cheaper, why not try to bring your own product to market? You'll be able to price it however you'd like.
Keep in mind, you'll need a warehouse to store your supplies, tools and inventory. You'll need a supplier for plastic tubs and an electrician to wire up your heat strips (for liability reasons, you probably wouldn't want to do this yourself). You'll need to hire someone to pack up your racks for shipment, someone to handle your sales and accounting, someone to run your website. Oh yeah, you'll need to provide insurance and benefits to all these people. Keep in mind you'll also need to pay your taxes on the income you get from these racks.
I hope you get my point. Businesses cost money to run. Products cost more than just the materials they are made from. Nobody works for free either.