I’ve worked in the funeral industry, and I assure you, it could never and would never happen.
Even really cheap, filing-cabinet-metal grade coffins (in the U.S. they are caskets) can be made to look decent at a viewing with flowers and embellishments.
I have heard of this when cremation is going to happen, they have the body in a coffin for the funeral then after that I think it would be reused but in those circumstances I don’t think the family is required to buy the coffin.