I think I am starting simple. I am leveling an area beside a patio that is 15x17 for a wooden swing. The retaining wall will be the red liplock blocks. The wall is going to be 15 feet long and 2 feet high. It will be capped off with same 2inch cap rock. I will be backfilling it with dirt then mulch on top. I know my mulch and dirt prices, but not retaing wall block. I read an average quote is 12 per block does this sound about right?