合理的利润空间在选择产品时一定要认真计算产品利润，否则会陷入低价没钱赚

Reasonable profit margins. <br>When choosing products, you must carefully calculate product profits, otherwise you will fall into the dilemma of low prices and no money, and high prices. Generally speaking, the profit of marine products should stay at 30%-40%; the profit of air products should stay at 20%-25%

Reasonable profit margins<br>In the selection of products must carefully calculate the profit of the product, otherwise it will fall into a low price no money to earn, high prices can not sell out of the dilemma. In general, profits from marine products should remain at 30-40 per cent;

Reasonable profit space<br>When choosing a product, we must carefully calculate the profit of the product, otherwise we will fall into the dilemma of no money at low price and no sale at high price. Generally speaking, the profit of marine products should be kept at 30% - 40%; the profit of air transport products should be kept at 20% - 25%<br>