What armies are the least expensive and what are the most?

Mostly posting this for my own curiosity, love 40k and have been eyeing age of sigmar for a while mostly due to A) liking fantasy settings and B) god the models are gourgeous. Probaly waiting to pick up a army until a friend of mine has finsihed collecting his 40k army so we can play it together.

Before then I was just curios to know what armies are considerd the "Cheapest" or cheaper side and what armies are considerd the most "expensive". Just consider what to pick when the times come (Of couse you should pick the army the looks the coolest but being indesive thinking with the wallet helps)

and how that compares to 40k, like the cheap armies (Custodes, Grey knights, etc) and really expensive armies (Sisters, Guard, genestealers and etc)