Good bunk bed:
There are 3 main things to look for when shopping for a "good" bunk bed that has a relatively inexpensive price point.
The first thing to look for is how the side rail that supports the bed is mounted to the ends. Typically, in this price range, the beds will be made of metal and certain types of mounts can squeak more than others. A system that has a full bolt through attachment is going to be the best because it acts a like a clamp on the post and will squeak minimally. The system that squeaks a lot will be one where the side rails hook into a bracket and are attached with only a small inside screw that keeps the rail from lifting. This system will also be less sturdy because there is not a clamp effect on the post.
The second thing to look for when shopping for a "good" bunk bed would be the support system. The best support system is a platform that is made of round tubes and is completely welded together. A cheaper support system will either have only a few slats or might have a wire type support.
The third thing to look for would be how the ends of the bed are constructed. The best way to build a headboard on a cheaper bunk bed is to have it completely welded together. The cheaper way some bunk beds are built is to clip or hook pieces together. Also depending on what kind of bunk bed you want it is going to be more sturdy with a leg that is solid from top to bottom. For a split-able end on a bunk you would want to know how those ends are connected so that it is more sturdy.
Better and best bunk beds:
When looking for bunk beds that are in the price range of about $299-$1499 there are many things to consider. In this price range quality can vary quite a bit. The more inexpensive bunk beds in this category will probably be made out of solid pine or a more heavy duty metal. The hardware and how you attach the ends to the rails will vary from bunk to bunk but shouldn't be drastically different. The best option for the better bunks with a cheaper price point is to do a solid pine with a 2x6 side rail and a slat kit that has at least half of the slats screwed down on each end. Here is an example:
HEARTLAND 2X6 HEAVY DUTY BUNK BED
If you are looking for a mid range bunk bed that is made well and is made of a good quality wood then you will want to look for something made of hardwood. The most common wood for this price range is rubber wood. Your price will be from about $399-$699. The negative thing to rubber wood is that it grows short and not very straight. Therefor the manufacturers have to splice a lot of small pieces together using finger joints. The quality is usually better than pine as long as the pieces being used are thick. Here is an example of a bunk made from rubber wood:
SESAME BUNK BED
The best quality bunk beds will range from about $699-$1499. Most of these will be made of a hard maple, Oak, birch, mahogany, or acacia. A select few will be made of cherry or hickory. Usually if you go to the right place you can get a hardwood maple bunk bed for around $799 depending on the style and size. These bunks will usually have full 14-16 slat support systems that are screwed in on every slat. They will also have center braces for the full size and some will even have center braces on the twin size for extra strength and support. Here is an example:
BEADBOARD BUNK BED
The bunk beds made of cherry or hickory will be on the higher price range because the cost of those wood species are typically a little higher. Just remember when looking and shopping for bunk beds if it says oak or cherry finish that doesnt mean its a good quality.