Trying to clarify what I meant by
In general, I would say the difference is that product development requires much more attention to maintainability and architecture than projects, which may be one-off solutions:
If you're a product company, selling a product named WhizBang 5.0, WhizBang 6.1, WhizBang X, WhizBang 2009, etc., you typically can't afford to start every new version from scratch. Your architecture has to be in a good shape. Otherwise you'll end up open-sourcing your product in a desperate move to avoid bankruptcy after your product releases have slipped severely for many years in a row...
Then again, if you're a stovepipe company engaging in a bespoke development project building a piece of software that automates some mandatory but non-essential part of your company's operations, you might not have too strong an interest to invest too much into a rock-solid, nuke-proof architecture. In other words, you're not expecting to need major changes into the software being built (and the contractor might have his own
profit margins in mind...) so the Good Enough bar tends to be lower compared to a product company.
Does this make sense?