Thorns,

the Lay price is generally only one click higher than the Bet price. For example, if the bet price was $3.00 then it was most likely that the Lay price was $3.05.

If you are showing a 25% LOT using Bet prices then the profit on Laying should only be a few percentage points less than the 25% which is impressive. However, I'm assuming the prices for your method are not in a high price range where one click could easily be $0.50 or more which could mean the difference of quite a few percentage points.