It's realism, not cynicism. I've absolutely been in situations like that where the sensible estimate is 5X what management is angling for and I know it's the case because we've done that exact thing (In this case, new hardware bring up) many times and with the inevitable problems, it always takes the high number. :/
I worked at a place where everything had to be gold plated. Some devs had an idea for a json driven form. It was super simple. Less than a week of dev time.
Management got it and an architect got involved. The project was taken from the original devs. The new team spent 2 months building a DSL, that didn't support mobile (so didn't meet the requirements). In the end it was canned.
The original 3 man dev team (Rails/JS/IOS) did a bit of skunk works, and built the original idea in 2 days. We had a good head of tech at the time so we deployed it and just kept quiet when we estimated new forms.
