The fees for involving the external auditor depend on the size of the council and the level of seniority compiling the response...
For councils with £25001+ the fee for the annual review is £200 rising to £3600 for authorities up to £6.5million. Hourly rates range from £105 for 'other staff' up to £355 for 'engagement lead'
So £1000 is entirely possible.
These fees are fixed across the board by the Smaller Authorities Audit Appointments board www.localaudits.co.uk/fees.html