The price of M0 and M3 variants are dropping dramatically. In November the price of a M0 chip with 64k flash + 8k ram has dropped to 1 RMB(0.15 USD) in China Mainland, and M3 (stm32f103 variants with 64K flash + 20K ram) dropped below 5 RMB(0.75USD).
The price depends on whether there is a alternative manufactured in China, Taiwan or Korea. If yes, you should wait, the price will drop, and the clones prices will soon become totally unprofitable. If not, the price will remain high and you should take action, for all the uncertainty will increase the shortage.