If you think about it, there are almost infinite different combinations of garage doors. You can mix and match color, material, size, add-ns, surface, insulation quality, windows, designs, and more. Because there is so much variability within the market, making a price estimate can be tricky and comparing garage doors from different companies may not always be as straightforward as you think. Two garage doors, while highly similar to the naked eye, could be made out of entirely different things, be differently durable, may include different varieties of insulation et cetera. Custom work can end up ringing up a pretty big bill, whereas some standard doors look as if they were made custom and are much cheaper.
Another thing to keep in mind is that safety features are not free. Most doors come equipped with the scanning electronic 'eyes' that detect a presence beneath the door and reverse it to prevent crushing. Some garage doors now come with a feature that prevents little fingers from getting caught in the spaces between panels. Some doors come equipped with alarm systems, like a burglar alarm in your home, and others come with physical padlocks.
If you have small children in your home, you may be more inclined to invest in some of these safety features, but in any case their inclusion should be a part of your cost analysis, as should the requisite electric garage door opener.