If someone raises chickens from eggs; pays for feed and cares for them until they are full-size, and then sells them, he has to pay taxes on that income, even though he already paid for the food and the upkeep. There's no double dipping here.

You can find an accountant who can give you advice on how to account for the cost of mining the bitcoin to reflect your effective cost basis (or wing it; the IRS has reasonably good instructions for this sort of thing).

If you go to Newegg and buy stuff, you are obligated under US tax law to pay the capital gains taxes based on the fair market value of the products purchased. If you go to a bitcoin meetup and sell with cash, you are still obligated to pay taxes.

Your legal obligations are clear; whether you can commit the perfect crime or not and get away with it is another matter.