What can cause an A/C to freeze up
Mine was freezing over and not cooling the house. I had recently replaced the filters so I made sure all the vents were open. I noticed there was no airflow so I checked the A/C coil up in the attic... I pulled the panel off and  it was completely blocked by lint. I used a wide vacuum brush and sucked all the crud off and now there's airflow again and the house is cooling down as I write this.
Cost, sweat! lots of sweat!