During our 4-week long July trip to north and south-west China, we found laundry in all small towns (pop 50K+).
As said by several prior posts, doing your own socks and undies was our normal practice (if time allows).
Due to 93F+ temp and 100% humidity, I changed cloth twice each day. We sent out wash-and-wear stuff daily. Found outside laundry service efficient, 24-hour turn-around, and folded. Pay when you drop off clothes. Average cost (samples only): 2RMB for socks and undies; 4RMB for pants and shirts; 7RMB for jeans. These prices are samples in smaller towns only. Bigger cities tend to cost a bit more.
Sorry, no personal experience for Hangzhou or Suzhou.