Kinda impossible to isolate due to Bitkit team and roadmap overlapping a lot with other teams. Bitkit was Synonym's first project, starting with just 2 guys. Today the core Bitkit team is 4 people, plus time from QAs, designers, legal, etc.

Is it cheap to create a production-grade wallet? Not really, the main costs are related to supporting Lightning.

However, Synonym is very lean in spending compared to typical startups. After 5 years, and tons of research in many areas, and currently at 30 people, we have spent less than $10M, mostly on Bitcoiner salaries. (Compare this budget to your favorite Bitcoin startup, which probably spends double our rate).

This has yielded multiple versions of Bitkit, an entire identity and web protocol, a LSP server and service, a scalable social app, a new payment protocol, a keychain app, a new credit protocol, etc, etc.

In the end, it would be silly to complain about any of our spending, because all if it is towards a goal of total user autonomy, making society, and Bitcoin, a better place.

We are not merely building a wallet, we are building the Atomic Economy.