If I remember correctly Shopify is something like 400k lines of Ruby on Rails code and 400 developers (i.e. one developer per 1000 LOC). Whereas I guess a 5k LOC codebase could be handled by a single developer.
That's a couple of weeks work.
EDIT: I'm being flippant, but to me a 400k code base is something 2 devs can put out in a few years. I'm pretty certain the present main code base I'm working on must be close to 400k and it's only ever had 2 devs working on it at any one time.
And we're always adding massive chunks of new functionality, and are regularly integrating with new third parties. And we total overhauled it last year to support i18n and it's now being regularly used in 3 languages and we can add more in literally a couple of days.
Ok it only handles hundreds of thousands of users, but I expect it to be millions within a couple of years and we're not even trying to load balance or anything yet.