An example of a constant cost industry, consider the production of birthday cake candles.
As the industry grows, it will use more workers, wicks, and wax, but because the industry is such a small part of the markets for labor and materials, the price of these inputs won’t change.
The long-run supply curve for a constant-cost industry is horizontal at the constant average cost of production.
At any owner price, the quantity of candles supplied would be zero because in the long run, no rational firm would provide candles at a price lower than the average cost of production.
At any higher price, firms would enter the candle industry in droves, and entry would continue until the price dropped to the constant average cost of $0.05 per candle.