Apple fans are serious. They will line up for hours to buy the newest version of the iPhone and they'll pay a lot for a 37-year-old computer. One of the few remaining original Apple I computers was put up for bids Monday, and auction house Christie's expects it to attract a winning bid of between $300,000 and $500,000. Half a million dollars is a lot for a circuit board built in 1976 without casing, keyboard or monitor. In fact, that kind of money could buy you 250 MacBook Pros. But, the Apple I isn't just any circuit board. It was the first product designed by Apple (AAPL, Fortune 500) co-founder Steve Wozniak who built it in his partner Steve Jobs' parents' garage. Only about 200 Apple 1 computers were ever built by Wozniak and Jobs. At the time, the design attracted the attention of Paul Terrell who owned a Silicon Valley store chain call Byte Shop. He bought the first 50 Apple I computers for $500 each and resold them for $666.66. In May, an Apple I computer sold for $671,000 at a German auction house, Auction Team Breker. Last year, one sold for $374,500 at a Sotheby's auction. Bidders have until July 9 to make an online bid at Christie's for the latest Apple I to go on sale. Other iconic computers from the 20th century, including a 1983 Apple Lisa computer, and a prototype of the first Macintosh laptop, are also included in the auction.