I hear you. I had large water bills too. Maintain 3-4" of organic mulch always to minimize soil moisture loss. It helps here in Texas, especially this last summer when we hit daily 100+ temperatures from June through late August. The top few inches dry out quickly, more so when planted by themselves. When watering, water deeply and use enough water to moisten the soil down to a depth of about 8". In sandy soils, you should be watering about 50% more than in non-sandy soils. If the soil is already wet, skip watering. Investigate the soil depression in the last two pictures.
