Why can't you judge whether a coin is expensive just by its price? Because price alone lacks context. One coin at $0.001 and another at $50,000 — by the numbers you'd instinctively feel the former is cheap and the latter expensive, but that's an illusion. Price is merely the result of market cap divided by circulating supply — a low unit price may just mean a huge circulating supply. To judge value and upside, you look at market cap (overall size) and the supply structure behind it, not the misleading unit-price number.
What's the difference between market cap and FDV, and why look at both? Market cap is "current price x current circulating supply," reflecting the market's overall valuation of the coin right now. FDV (fully diluted valuation) is "current price x max supply" — the valuation assuming all tokens already circulate. The gap between them reveals future supply pressure: if FDV is far larger than market cap, lots of tokens are still locked and unreleased, and when they unlock they'll dilute existing holders and create sell pressure. Looking only at market cap and feeling it's cheap while ignoring FDV is a common beginner trap.
How do you read circulating, total, and max supply, and what's the use? Circulating supply is the amount tradable in the market now; total supply is everything issued so far; max supply is the most the coin will ever have. The most crucial for you is the gap between circulating and max supply — that gap is the supply that will keep unlocking and entering the market. The bigger the gap, the heavier the future dilution and sell pressure. A coin with only 10-20% of its max supply circulating may look scarce with a unit price propped high, but as the remaining 80-90% gradually unlocks, existing holders are likely diluted.
When actually reading a coin's info page, how do you link these numbers into a judgment? Follow four steps. First, don't be misled by unit price — go straight to market cap and grasp its overall size. Second, compare FDV with market cap: if FDV is several times the market cap, remind yourself a lot of supply awaits. Third, look at circulating as a share of max supply: the lower the share, the higher the future dilution risk, and you'd best check the vesting schedule. Fourth, check 24h volume for liquidity: a coin with too-low volume is hard to get in and out of even if the data looks pretty. Make these four a habit and you'll never again enter on unit price or hype alone.