The price is not the reason it doesn't have a Retina display.
Here is where the tech is as of now:
iPad 3/4 require additional graphics capability to power the display. This uses a lot of power.
The displays are also power hogs.
In order to put a Retina display in a tablet, and have a battery that lasts more than 3 hours you need to include an enormous battery. Enormous batteries require more space and add a ton of weight. You could add thickness to accommodate the physical size of the battery, but it would end up weighing just about the same as the full size iPad.
People are loving the iPad mini because of it's light weight and super thin form factor. If you're going to make it thick and heavy, what's the point of making it at all?
Over the next 1-3 years we'll see IGZO displays become usable in mass quantities. When that happens, power consumption will be reduced dramatically. We'll also see Apple's standard ARM chips become more capable at pushing lots of pixels. When those things happen, we'll see a Retina display in the mini. Until then, we won't.
Even when we do see a Retina mini, the display will likely be in the ballpark of 1600x1200 (+/- a few dozen pixels each way). A more powerful standard ARM chip (like iPhone) will be able to power that resolution much faster than 2048x1536. It will also require less power to do so.
Right now there are effectively 3 resolutions for iOS developers to work on (iPhone 3Gs being dead). Adding a 4th wouldn't be a popular idea. Within 2 years at the most iPhone 4/4S, old iPod touch will be dead, along with their resolutions. iPad mini will have gained a significant user base and developers will want to build for it as a result, so the new resolution won't be a huge problem.
Factoring all those things in, it's clear that there are legitimate reasons for there not being a Retina display in the mini. It's easy to say it's all about money and greed, but it just isn't.