Have you got an old Apple Mac computer sat in a dusty corner of the attic? If you do then you might be sitting on a goldmine.

Apple has developed a cultish following over the years and that means that the really old computers defy conventional wisdom. A 20-year-old PC is usually nothing more than a paperweight, but this is simply not the case with classic Macs.

It’s unlikely that you’ll have the best of the bunch; the original Apple 1. Just 200 of them were produced and just 50 are thought to have survived until now. Auction prices for the lucky few have been eye-watering, with one computer fetching £431,000 ($671,000) in Spring 2013.

That has since been usurped as the most expensive Mac ever by a pre-production Mac Pro that was auctioned off recently for £628,000 ($977,000). But assuming you don’t have either of those, and you probably don’t, how much could your system be worth?

The 128K All in One, released in 1984, is one of the major classics. Prices of £1,300 for a mint condition example are all too common, which means this basic computer could pretty much fund a new iMac. If you are one of the people that bought a Newton Messagepad then it may have been a disaster at the time, too, but now they are worth upwards of £800 to collectors.

The Apple II, which was sold from 1977 to 1993, goes for £300 on eBay in working condition and there’s a market for more or less every older system. Even the old desktops like the Quadra 840av can command more than £600 from bid-happy collectors on the auction sites.

All of this pales into insignificance when compared to a factory-sealed first generation iPhone with a ‘good’ serial number, though. If you have one of these, you could be sitting on a £9,000 goldmine if you find the right buyer.

So if you have an old Mac gathering dust in a corner, get it out, fire it up and then get it sold. You might be surprised how easy it is to sell Apple Mac classics and fund your next purchase.