Australians who squirrel away their old mobile phones, computers and video games in cupboards or garages could be sitting on a small fortune without realising it. Obsessive collectors around the globe are paying thousands of dollars for tech products that other people store away and forget after buying a newer version. For instance, a 2007 iPhone with its original packaging can now sell for more than $12,000. Collectors' fever also applies to old computers and video game disks. Rare Nintendo games sell for tens of thousands of dollars, and original Apple Macintosh 128K computers are being offered on eBay for more than $4000.

Such examples are exceptions rather than the rule, because the principle of rarity applies to old tech in the same way that it does to stamps or coins. If you have a limited edition of a sought-after item – or holy of holies, a prototype – you're in luck.

A 1987 Telstra ad for Australia's first mobile phone. The Walkabout was quickly nicknamed "The Brick". They are now worth as much as $5000.

Proof that checking is a good idea hit the news recently when a mystery woman in California dropped off a vintage Apple I computer to a Silicon Valley recycling depot, which later announced she'd tossed out a collector's gem worth more than $US200,000.

The company is offering her a $100,000 check if she turns up to claim it, but it could be worth 10 times that amount. Only 200 or so Apple Is were made in Steve Jobs' garage in 1976, and one sold at auction last year for almost $US1 million.