Inventory Audit Report doesn't match up with Inventory in Warehouse Report

These two reports use different prices. 

The inventory audit report updates the last calculated price list. The inventory Audit Report using the actual price coming from inventory at the time you run the report.

The inventory in warehouse report: The system valuates the warehouse inventory using the price of the item from the price list you specified. 

STANDARD PRICE
Valuation using a standard price has the following features:

• All inventory postings are carried out at the standard price
• Variances are posted to price difference accounts
• Variances are updated
• Price changes can be monitored

If a material is assigned a standard price (S), the value of the material is always calculated at this price. If goods movements or invoice receipts contain a price that differs from the standard price, the differences are posted to a price difference account. The variance is not taken into account in valuation.
MOVING AVERAGE PRICE
Valuation using a moving average price results in the following:

• Goods receipts are posted at the goods receipt value.
• The price in the material master is adjusted to the delivered price.
• Price differences occur only in exceptional circumstances.
• Manual price changes are usually unnecessary. However, they are possible.

If a material is assigned a moving average price (MAP), the price is automatically adjusted in the material master record when price variances occur. If goods movements or invoice receipts are posted using a price that differs from the moving average price, the differences are posted to the stock account; as a result, the moving average price and the value of the stock change.

Therefore, if you see these two reports not matching up, SAP is designed that way.