In reply to Chris_V: The Miata is one. I can name many FWDs that are light and tightly packaged. In most cases as we have here, there are exceptions.
Most RWD econo-cars were left over remnants of old car design. I'm not saying bad, I'm saying that there are savings to be had buy going FWD, the market has shown that. Many of these cars are also body on frame, but no one would defend them for that.
RWD certainly costs more to build and therefor costs more to buy and more to own. You have a driveshaft. You have a separate casing for the rear-diff. You have more mounts; having separate mounts for the engine, trans and rear-diff.
On the assembly line you have added a couple of more steps. You will have to have someone put in more bolts and the powertrain will take up more space as it is brought towards the engine. I'll grant you are economies of scale the RWD option may seem small, maybe $20. But there are accountants that would count the beans and talk to marketing. In the end, they'd tell you, you'll lose .02% of sales but make you're investors a profit. You tend to choose the path that seems safest.
The Miata is a great car and very durable. But as a whole, more parts means more parts can break. From a manufacture's point of view, there has to be some infant mortality with driveshaft joints and benefit in terms of doing warranty service (I know the whole Saturn powertrain comes out as one unit with little work). Such thing factor into price.
RWD drive cars can be tightly packaged and inexpensive to buy an own, to be reasonable the Miata is a great car and while a great example, proving it can be done, it is the only example; Perhaps proving just how difficult a good, inexpensive, tightly packaged RWD can be. In the end a FWD CRX Si or Civic Si made out of leftover parts at the Honda plant can still hang.
Don't get me wrong in my FWD defense, I love RWD and FWD, I sign myself to no camp, but I race an know FWD pretty well. FWDs are capable of amazing things as long as you aren't wanting to land a ton of horsepower onto the ground.