At the end of the day, asking "How much is a Zone 1-2 Travelcard?" is like asking "How much does it cost to have a functioning social life in London?" It’s a lot. It’s a constant negotiation with your wallet and your willpower.
But it gets you from your flat, past the man selling slightly sad-looking croissants, to your desk, and back again. It’s the price of the dream, or at least the price of not walking through Clapham in the rain. So go ahead, buy the card. Just don’t look at the receipt. For your own sanity, just don’t look.