I calculate it at 52 cents per panel (40 lbs a panel)

Source for the cost:

https://docs.nrel.gov/docs/fy21osti/74124.pdf one study found that disposal tipping fees at non-hazardous landfills ($26/U.S. ton) can cost less than $1 per module and less than $5 per module at hazardous waste landfills ($175/U.S. ton)