Acrylic ice cubes are used for display and photography purposes. They are a non-edible and non-cooling agent.
They are used in displays because they are indeed not real and they are used in photography for their crystal clear appearance. These are better than ice except for the whole no eating and no keeping cold bit.
You can make actual ice that is as clear as what you'd get in a restaurant but that takes a little bit of a process and is not worth the effort for photos, save yourself a little time and just buy them if you can use the fake ones.
Photographers also use glass ice cubes as well as acrylic. These fake glass ice cubes are a bit expensive and do not float well but since they are reusable if you have a reason to use them more than once they will save a lot of time and effort.
Whether they are perfectly square, oddly shaped, or glowing from a led insert there is an ice cube to be had. There are a number of online retailers that carry these and you can find them in specialty shops in you'd rather pick them up at a brick and mortar store. You won't find these at your local Wal-Mart but if you live in a large city there will be a shop that you can find that will carry them.
The price of acrylic ice cubes will vary depending on how many you want to buy, where you buy them, and how much the shipping and handling is if you decide to purchase online. You can get a couple pounds for around 25 dollars and they go up for more.
If you tend to be an arts and crafts kind of person, if you have a bag or 2 of these on hand, there's no doubt you'll come up with some clever way to use them. Most people simply do not have them on hand and need to make a special purchase if they have a plan for them.
Good luck finding and using your Acrylic Ice Cubes I'm not sure what your plans are but I'm sure it'll be a wonderful display or photograph. Heck maybe it'll be a photograph of a displayâ€¦ you never know.