Real Estate taxes can vary even if 2 properties sell for the exact same dollar amount. If a homeowner has made improvements while inhabiting the home a permit may be required for these improvements. Once the permit is filed the township will come and inspect the work on the property to assure building code requirements are adhered to. This can generate a new assessment on the improvements therefore creating a tax increase. It is important when researching the purchase of a property in a neighborhood to have your Realtor do a search of other homes in the direct vicinity and provide you with the recent taxes for other properties nearby. This will give you a comparative before you decide to purchase.
I think I already answered this question on your other post - but they can vary from 4-10k on average, depends on the part of Yardley you are looking in.. They will be less in the Boro and outlying areas of the Boro, higher in Lower Makefield Twp. If you have a specific property in mind, let me know and I'd be happy to look it up for you.