How much does a private key cost?

The query on many minds these days revolves around the cost of a private key in the realm of cryptocurrency. Could you elaborate on the various factors that influence the pricing of a private key? Is it a fixed cost, or does it vary depending on the type of cryptocurrency, the complexity of the encryption, or the security measures taken? Is it advisable to purchase a private key from a third-party vendor, or is it safer to generate one's own? And finally, what are the potential risks involved in obtaining or handling a private key without sufficient understanding of its intricacies?