It does add up, but (a) I wouldn't put pedals at the beginning of that list, and (b) I wouldn't put bike-specific clothing on the list at all; spandex is overpriced overkill, especially for a new rider; except depending where you live and how often you plan to commute, you might need to consider rain gear.

Helmet for sure, red rear blinkie next after that, front headlight can wait a few months until it starts to get dark early, lock if your employer won't let you bring your bike inside. And yes you want to be prepared to repair a flat on the road, so that means a seatbag with tire levers and a patch kit and/or spare tube; also a pump (probably frame-mount).