If you just held them as a lifetime investment, you might get away with it.
If you were to hold for a few months then sell, you would need to pay capital gains tax then, obviously with your gain being 150,000-7500 (because technically you sold the item for $7500)= 142,500. If you got caught not paying, you would most likely get charged with tax evasion.
In other words, you owe the capital gains tax at some point. I'm not positive on it, but you would have to file proper paperwork for a 1031 exchange tax shelter for real property being exchanged in lieu of profit as an investment, of course, if the item you are selling was some type of investment vehicle (which if you were to claim the full value of the gold, you may be able to claim it as an investment vehicle, but doubtful).
In other words, in my professional opinion, you are playing with fire.
(I am not an expert on 1031's. I have been involved in one, but it took a team of lawyers and a CPA that specializes in exchanges, so it's not a typical thing)