It is a common practice almost everywhere I work.

When Photoshop is too expensive, we get Powerpoint-driven development instead.

While Photoshop is a terrible starting point, if it gets avoided primarily for cost reasons, run away anyway.

It's not a cost reason, most likely it's management doing the mockups. Powerpoint it's all they know.

That might not be so terrible. GP was suggesting it was due to cost, which is a "run away like the building was on fire" signal, IMO.

If all management knows is powerpoint, that's what they should use to communicate their ideas. It's no different than if all they knew was a napkin and pencil sketch.

I is due to cost. I am aware of a few projects that were done with trial versions of the software stack, almost all the way up to a few months before delivery date.

Well, to be honest, in the last year a lot of designers have moved to Sketch or similar alternatives, but it's still very common to work with plain screens as start point when working as contractor.

Sketch-driven development is not that much better. It is easier to get from design to app, but then edge cases and real data start to interfere with vision and you are doomed anyway.