I have written about STM32F105RB and why I chose this before. Sample prices on AliExpress do variate, but I noticed some batches of STM32F105RC for 1.8 USD each so I purchased 10 of them – they arrived today and I will stick one of them on a breakout board later. ST’s own price for this is 3.- USD, so I am not sure why I get these for almost half the price.
The sellers on the RB version advertise these as the 32Kb Versions, but I am not aware of a similar scheme on the RC. Frankly I don’t care either as long as they work as this is for prototype’s. The RC version have 256Kb Flash and 64Kb SRAM.