It is apparent to me that there are legal questions that can not be answered on this forum. Your townhouse community very likely has rules that must be taken into account. I suggest you take this matter to an attorney immediately. Don't bother to talk to your neighbor, he's obviously not interested in resolving this or he'd have come to you when the problem first arose. I would note that if this repair was as simple as you describe, the charge is grossly out of line. Repairing a PVC or poly pipe is extremely simple and requires nothing more than digging, cutting out the broken piece, and splicing in a repair section.