Once agreement occurred, your word is your bond.
Yes, it is in writing. OP admits it was part of the deal in his first post.
It amazes me that people can justify poor behavior. If OP just took care of delivery at the time of transfer this would not be an issue. He made a mistake that he should correct.
If you go to the grocery store, buy oranges, and leave them on the counter, but come back 8 months later demanding your oranges, do you think the grocery store is going to give them to you?
lol no. You crazy
If you want to split hairs, OP should charge buyer storage fees on the cluster since buyer failed to pick it up.