Hi jirvinross,
The first place I would start your research is the mattress shopping tutorial here which has all the basic information, steps, and guidelines you will need to make the best possible choice.
If your budget range is about the same as the Casper price then yes there are certainly others that I would consider depending on which types of material you tend to prefer (memory foam, latex, polyfoam, innersprings etc). The tutorial post includes several links to some of the better online options I’m aware of. Many of them are also factory direct manufacturers that have their own factory and have less middle men than Casper which doesn’t have their own factory and is a reseller that sells mattresses made by a foam fabricator (or what is also known as a “cut and sew” mattress).
If you let me know your city or zip code I’d also be happy to let you know about any of the better options or possibilities I’m aware of in your area as well.
Phoenix