Preparation for future photovoltaic?

I'll jump in here with a question. What - roughly - does it cost to have empty conduits installed for the photovoltaic system? Just to have a rough idea.

Thanks!

I also had the electrician lay thick cables. My photovoltaic installer did not want these, but preferred to pull his own cables. So better to build empty conduits or photovoltaic right away.

For what reason? Did he pull different cables technically or did he just not want to lose the profit from his new lines?

Something with direct current and alternating current, I didn't question it further, I had the conduit. Maybe for safety reasons? The voltage is clearly higher, the two solar cables in the conduit each have only one conductor.
Furthermore, there are no unnecessary connection points, the cables go directly from the roof to the inverter.

Lay only empty conduits, the cables will be brought by the solar installer anyway.

Just lay empty conduits, the solar installer will bring the cables anyway.

But you know what crazy prices installers sometimes charge for cables. Since I lay all my other cables myself, why should I make an exception for photovoltaics?

Since it's also about warranty, I wouldn't include any third-party components in my system either.