Every key gives a dragonstone. The rest is a roll, not a wage. Opening crystal chests can show a positive average. That does not mean your next ten keys will make gold. Before you buy keys, separate expected value from the loot you are guaranteed to receive.
OSRS-GE is a free Old School RuneScape Grand Exchange tracker. Prices come from the OSRS Wiki Real-time Prices API and refresh every minute. Every margin shown subtracts the 2% GE tax, capped at 5m gp per item, and respects each item's 4-hour buy limit, so you see the profit you can actually make. Use the calculators to compare flipping, overnight offers, High Alchemy, herb cleaning, decanting, Plank Make, tanning and other money making methods, and read the guides to learn margin checking, how to avoid fake margins and when to trade.