Which ones, if you remember? Same price as in the 80s is still discounted, inflation-adjusted.
Or this TRS80 for £500 https://www.ebay.co.uk/itm/Radio-Shack-TRS-80-MODEL-100-PORT...
Of course they might not sell for the listed price, there are other listing with lower bids. I don’t know a good way to get an accurate figure for what things typically sell for on ebay etc.
It will then show only recently sold listings along with what they sold for. Completed listings that didn't sell because they were listed with unreasonable prices will not show up.