Best Time to Purchase Internal Airline Tickets in China?

Hello, I am looking to purchase airline tickets and I found these prices on Travel Zen. Below is the price listed for one airline ticket, one way only:
Friday May 2nd
Shanghai Hongqiao to Luoyang, $87 USD
Monday May 5th
Xian to Guilin, $85 USD
Saturday May 10th
Guilin to Shenzhen, $75 USD
Is this a good price? Should I buy the airline tickets now, or wait a little longer to see if the price goes down? Thanks in advance for your advice!