The store has bought a batch of goods and sold them at a 40% markup. After 80% of the sales were made, in order to sell them out as soon as possible, it was decided to dispose of the remaining products at a 50% discount, and after all the products were sold, an additional tax of 150 yuan was suddenly imposed, which made the actual profit margin of the store only half of the expected profit rate. How much is the purchase price of a batch of goods? (Note: additional tax is counted as cost)
商店进了一批商品，按40%加价出售．在售出八成后，为了尽快销完，决定五折处理剩余商品，而且商品全部出售后，突然被征收了150元的附加税，这使得商店的实际利润率只是预期利润率的一半，那么这批商品的进价是多少元？(注：附加税算作成本)
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) * 0.5 * 150</gadget>
<output>30</output>

<gadget id="calculator">150 + 30</gadget>
<output>180</output>

<gadget id="calculator">(2/5) * 0.5</gadget>
<output>0.2</output>

<gadget id="calculator">1.26 - 1 - 0.2</gadget>
<output>0.06</output>

<gadget id="calculator">180 / 0.06</gadget>
<output>3_000</output>

<result>3_000</result>