Need Advice For Chinese First Day Folder Sets In Ebay

Hi everyone,

Happy new year. I am new here. I found an ebay seller who is selling sets of Chinese first day folder. One of them is the sets (5 in total) first day folder "The first anniversary of the death of the great leader Chairman Mao". (The product title is "set China First Day Cover FDC folder J21 1977 stamp Chairman Mao Ze Dong"). What surprised me is that the current bid price is only about $15 by two bidders??

Since the Chairman Mao is always the hottest topic among CHINESE stamps. I am thinking to bid them around $70-80. Do you think does $70-80 work, or do I need to increase to $100+?

There are 2.5 days remaining for this bidding. I am looking forward for your suggestions. Really appreciate it! Thanks!