Everything has dollar/currency value.
You could trade that $900,000 painting for a house. You would face the same tax consequences of paying $900,000 worth of Bitcoins for a house.
No dollar has to be exchanged. It is just more difficult for the IRS to track the gained value of a painting when it was evenly traded for a house. Same with Bitcoins and never converting them back to dollars and instead using them to purchase things.
As for me, I claim every single thing for the wonderful IRS man who may potentially be reading this. I file every form and audit every transaction I make at the end of the day keeping detailed records of everything so that I am in compliance.