Use this tag if you are enquiring about the cost of systems, either at a specific time-point in the past (such as when they were released) or now (if you're looking to purchase).
Examples when using this tag are
What was the cost in Australia for the Sinclair ZX80 when it first came out?
I'm looking to buy a TRS-80 Model 4D to round out my collection. What can I expect to pay for such a beast?