Depending on what kind of editing you're doing, the rMB might not be the best solution because, among other things, it's passively cooled (no fans) and on extended tasks is going to slow itself down to keep temperatures under control. My experience suggests potentially a 20% hit, compared to a 13" rMBP. Ports might or might not also be an issue. You can deal with that by using the $79 power/video/USB-A dongle and a USB 3.0 hub, but that might not suit you.
If you compare the rMB to a 13" MBA with the same basic specs (RAM and SSD), they are priced the same - but the rMB has a retina display. So, pricing is really not out of whack. It's just that you can get MBAs that are configured with 4GB RAM and a 128GB SSD and skinny the price down. Whether 4/128 will really suit you is a different question that different people will have different answers to.
You didn't say what you're editing, but if color accuracy is important, you should really consider the rMBP. For most purposes the display is merely "nicer," but for color-accurate work it is clearly the better answer.