The title is misleading. $135 is not "money saved", it's "money not spent on fossil fuels" (even for that I couldn't find how it was calculated by solarpowereurope, but the number seems plausible).

To the discussion of whether $50B/y is a big figure or not. EU has around 400GW of PV installed. Cost to install per 1kW ranged between $600 and up to $4000 because a big chunk of that capacity was built when prices were much higher. If we consider average price at $1000 this means $400B on capex alone + yearly operational expenses. It can still be profitable (assuming current PV prices can be sustained + installed capacity doesn't grow faster than storage) but it's going to be many years until the investment is recouped and it starts to actually "save money for Europeans".

In any case, of course it's still nice to depend less on imported oil, even if not for money savings.