How expensive is a CSGO key?

Excuse me, could you please elaborate on the pricing of a CSGO key? I'm curious to know how much it typically costs and if there are any factors that can affect its price. For instance, does it vary based on demand or are there any promotions that offer discounts on these keys? Additionally, are there any risks associated with purchasing keys from untrusted sources? I'd appreciate any insight you could provide on this topic.