anywhere from 50£ upwards ( to the americans thats about 75$ ish up to the thousands... reallly depends on the following
a- lining ( plastic lining .pvc, polythene or butyl lining) from 50p a sqft upto £5 a sqft
b-if u use preformed bases ( from £40 , to a nice large one £ 970 )(they do go higher)
c-what kind of pumps and filtration u use,( whether u use a uv filter or foam filter)
d-fish stock and plants,