How does a verbal agreement , not written contract, hold up when it costs more to do the job in the end?

I am a landscape contractor. I did a job without a contract, just verbal agreement. The agreement was to do the job for $8500 and lighting for $1000. I know I told him it would be hard to have much lighting for $1000. I did tell him I do not bid jobs of the unknown problems. I am sure he heard what he wanted to hear. But that I thought I could do it for $8500. At the first day or two of the job, we encountered difficulties that I knew would make it hard to get thing done within $8500. I did not mention anything at that time about how many hours we worked. We continued on the job. And the cost was about $5330. But the labor ran us over 162 hours and that tallies more than $8500. Then the lighting materials were about $1000. But the installation cost more. Near the end the client ask for some trees. I take his wife to my wholesale nursery and we buy $1735 worth of trees. I never talked about landscape stock until this late in the job . We have to move these trees with a bob cat and tree carts . We even transplant a tree . And need soil, compost , fertilizer and mulch. He sent a certified check for $8500 and another $1735 stating trees and landscape paid in full. However , the materials alone cost me more. I can’t even cover the cost of material s and labor. I am in debt $10000. Should I file a mechanic’s lien with success of getting enough money to recover?