I make my own breadboardable ARMs using cheap converters. I only need a couple for prototyping. ARMs from ST can run for years on a single AA battery and have

I make my own breadboardable ARMs using cheap converters. I only need a couple for prototyping. ARMs from ST can run for years on a single AA battery and have nowadays very easy tools. Probably you are missing understanding of whole range of ARM chips, these start from couple kB of flash and hundreds of bytes of memory.