The label tells you what is inside. Artist paints list their pigments on the label, and most colors are made from a single pigment. That is what makes them predictable to mix.
A pot is a finished recipe. Hobby paints are built to cover in one coat, so a pot is usually several pigments, often with white or black added, plus a matting agent. Mix two pots and you also mix their hidden white and black, which is why pot mixes so often turn dull or dark. Single-pigment paints stay clean.
Is it cheaper? Per milliliter, artist acrylics cost less than hobby pots, and student lines a lot less. For a handful of colors the difference is small and pots win on convenience. Mixing pays off when you need thirty colors, or one no pot sells.