Alter some Images

Hello. I have 60 folders, each of which contains 6 .png images. The images range in size from 152 to 354 MBs each. I need a 50% reduction in image size in each file (less reduction in smaller files is acceptable) in a way that preserves: (1) page size (2) colors (3) transparencies (4) folder hierarchy A knowledgeable person will batch process this. I have uploaded sample files from a single folder, below. The folders are organized by the first four letters and the High/Low condition after the hashmark. I encourage bidders to show me what they can do. I will not respond to auto-generated proposals. I will award the project to the person who does the best job according to these standards for the most reasonable price. This is a simple project, which I expect the bids to reflect. Thank you