That depends on what you need:

How many do you cook for?
How many servings do you want to be able to make?
Do you need to be able to make roasts during the week or just casseroles?
Do you prefer to cook budget friendly dishes that taste amazing?
Do you need to cook from scratch to avoid commercial additives?

Owning a crock pot helps you stretch your food budget further as it produces better flavored and textured beef meals when the cheaper cuts are used. You will save on your electric bill too; your crock pot set on low uses...