None of those people you spoke to sound like lawyers. It won't cost six figures to have a lawyer send a letter. Your competitor might not like the six figures prospect of defending themselves.
Actually they were business people who have been through this battle before spending in the six figures to defend their marks (along with my brother who is a patent attorney). But yes, you are correct that sending a letter is the first step but if that step is ignored then the next step will cost money...and too much money for a single developers side project!