Perhaps more mysterious than the stealthy look of Apple’s upcoming Mac Pro desktop is its price tag, which has yet to be announced.Apple detailed some of the specs, and even showed off prerelease versions of the hardware to attendees at its annual developers conference earlier this month, but there are still many unknowns as to just what Apple will put inside the machine -- details that have a dramatic impact on what it costs to buy one.So how much will the machine -- previous models of which have, for a decade, hovered around a $2,500 entry-level price tag -- cost when it arrives later this year? Based on some rough estimates of comparable hardware, components, and labor, just the raw cost of the machine could total $2,800, the firm said. That’s $300 more than the price Apple sells its existing, entry-level model for. Ramp it up with a higher-end processor, more SSD storage and RAM, and that could climb to $4,755. None of this, by the way, is taking into account the extra cost that goes on top, where Apple makes any profit.Why is the price so hard to pin down? Many of the components that are going into the machine have merely been stated by Apple, but not detailed. That includes three of the most important, and also most expensive, parts: the processor, graphics chips, and flash storage, which are all bleeding edge.Apple has said it plans to use Intel’s latest Xeon E5 series chips and AMD FirePro GPUs to power the machine, both of which could send the cost up drastically, depending on what configuration Apple begins with at the entry level. Those Xeon chips, for instance, can go well past $2,000 (though Apple gets discounts from buying in bulk). The graphics cards could be even more, as Apple is making dual GPUs a standard feature. Also unclear is built-in storage, which IHS expects to start at 512GB.