Product price in search results is shown according to the currency which is set up as the default one in the BigCommerce admin panel. To check the default currency setting go to Dashboard > Store setup > Currencies.
Searchanise used the Currency display settings. Click Edit to see them.
To change the currency format in the Searchanise widgets do the following:
1. Change the Currency Display settings for the default currency.
2. Go to the Searchanise admin panel.
3. Click FORCE RE-INDEXATION and wait until it is finished.