If you are excavating a 1/4 pond and are going to use a synthetic liner and a supplemental water source then you can basically dig it wherever you want. If you are not doing this, than you need to worry about watershed, soil composition, topography and multiple other factors. I would do a google search of this forum on "selecting a pond site" as this has been discussed many times. Feel free to post pictures as these can be very helpful, and ask away with any questions. Cost varies by region, but I have seen from $1-2/cubic yard of dirt moved. good luck