Other properties not involved in the transaction are not counted. Before all transactions, Miss Wang's property had a pair of shoes, 60 yuan (a pair of 30 yuan and a pair of 60 yuan), real money 100 yuan (returned to neighbors), * * * 160 yuan.

After all the transactions, there are real money from 90 yuan (one shoe was sold to 45 yuan and one pair of shoes was sold to 90 yuan, so we found a customer 10 yuan, leaving 90 yuan), counterfeit money of 100 yuan, and 90 yuan.

So the loss is 160-90=70 yuan.

Step by step:

1. When the customer bought shoes, Miss Wang gave a pair of shoes and got 100 yuan counterfeit money. At this point, 60 yuan is gone.

2. Find a neighbor to exchange real money 100 yuan. At this point, I earned 100-60 = 40 yuan.

3. Give the customer 10 yuan. At this time, earn 40- 10 = 30 yuan.

4. Return the neighbor 100 yuan of real money and silver, and the loss due to shading 100-30=70 yuan.

The results of these two methods are the same.