PM can't make money for some people, and a significant part of them don't lack judgment of events—they just don't know how to place orders.

Specifically:
Polymarket uses a limit order book (CLOB · central limit order book), not an AMM (automated market maker).
The 0.51 you see is the current lowest sell price, not a "market price."
Eating at market price = scanning upward one level at a time.
For example: Market depth is $200 / 0.51, with prices above at 0.52 / 0.55 / 0.6...
If you place a $1000 order, the average fill price might be around 0.56.
5% hidden slippage.
You see the event clearly, but your PnL is still negative—the root cause isn't misanalysis, but that your order size exceeds the market depth.
Three common pitfalls for beginners:
1. Default to market orders → sweeping the entire order book
2. Looking at the spread (price difference) without considering depth → narrow spread like 0.51/0.52, but each level only $50, so you can't fill it
3. Not paying attention to taker fees → Polymarket fully implemented taker fees at the end of March (fees for takers, ranging from 0-1.8% depending on category), which over time eats into margins
Correct approach:
- For markets with good liquidity (daily volume > $10K ): place limit orders near the best ask (best selling price) and wait for makers to match
- For less liquid markets: eat in batches, only consuming 50% of each level's depth at a time
- Always check the order book depth first, then decide on order size
——
I personally experienced early failures with prediction-trader: when the H36 strategy launched taker fees on 3/31, the win rate (WR) dropped from 69% to 65% in those two days, and PnL immediately fell to -$58.
The signal didn't change; it was the fees that ate away at the margins.
A common misconception among centralized exchange (CEX) traders—buying at the listing price on CEX is smooth, but on PM it's completely different.
Want to see the order book depth (how much is hanging at each price level):