Well in my personal experience the salary of senior devs in very early-stage startups i've been involved with in NYC get around get about 150K + options (text processing, machine learning, AI-stuff). With 2 incomes and some savings put aside, certainly its affordable, much more so than SF from what i've seen. The dev salary here may be higher because they need to complete with wall street firms, and there are overall less very senior devs in NYC compared to SF.