Under Directive 451 the appraisal is done by a certified appraiser who visits the property and draws it, independently of the bank's information. The bank must list in your approval in principle the appraisers it works with in the property's area. It may charge you only when the loan's conditions require an appraisal.
The appraisal matters because the loan amount is based on the property's value. In practice banks generally finance against the lower of the purchase price and the appraisal, so ask your bank how it will apply it to you.
The pitfall is an appraisal below the price: you must cover the gap with cash. If another bank had an appraisal done by an appraiser on your bank's list within the last 90 days, ask to use it; the bank may not unreasonably refuse.
Example
The price is ₪2,000,000 and the appraisal ₪1,900,000. If the bank lends 75% of the lower figure, the loan is ₪1,425,000 instead of ₪1,500,000, so you must add ₪75,000 to your own funds.