The cost depends on the depth of the water more than anything else. My mooring consists of a block of granite (not part of the seabed) with a 30' length of 1-1/8" chain and then 40' of 1/2" chain. The 1/2" chain is supported by a float and the pennant is attached to the end of the 1/2" chain. My mooring is in 16' depth at low tide.

A lot depends on the type of mooring anchor you have. Granite blocks have the advantage that they last a long time. Steel mushrooms are cheaper, but only last 10-15 years