An E-commerce website offers cashback of 15% on the marked price of a certain item and earns a profit of 19% on it. If the difference between the cashback offered and the profit earned is Rs. 150, find the cost price of the item.

Given:
– Cashback offered is 15% on the marked price.
– Profit earned is 19% on the cost price.
– The difference between the cashback offered and the profit earned is Rs. 150.

1. Let the cost price of the article be Rs. \(x\).

2. The selling price (SP) of the article is 119% of the cost price (due to the 19% profit):
\[ \text{SP} = 1.19x \]

3. The marked price (MP) of the article is obtained by dividing the SP by \(1 – \text{cashback rate}\):
\[ \text{MP} = \frac{\text{SP}}{1 – 0.15} = \frac{1.19x}{0.85} = 1.4x \]

4. The difference between the cashback offered and the profit earned is given as Rs. 150:
\[ \text{Cashback offered} – \text{Profit earned} = 150 \]
\[ 1.4x \times 0.15 – 0.19x = 150 \]
\[ 0.21x – 0.19x = 150 \]
\[ 0.02x = 150 \]

5. Solving for \(x\):
\[ x = \frac{150}{0.02} = 7500 \]

Conclusion:
The cost price of the item is Rs. 7500.