Give the average number of cities within markets that had a low market estimation larger than 10000?
SELECT avg(T2.Number_cities) FROM film_market_estimation AS T1 JOIN market AS T2 ON T1.Market_ID  =  T2.Market_ID WHERE T1.Low_Estimate  >  10000
SELECT avg(T2.Number_cities) FROM film_market_estimation AS T1 JOIN market AS T2 ON T1.Market_ID  =  T2.Market_ID WHERE T1.Low_Estimate  >  10000
[{'avg(T2.Number_cities)': 209.0}]