Buying a bungalow, adding an extra floor, and renovating - Is it worthwhile?

The price from the seller is currently over 600K, the standard land value for the 1050 m² plot is just over 400K. For me, however, the house has no residual value of 200K, so the price would have to come down considerably. There are hardly any single-family house plots on offer, the plots 500m further have a standard value of 600-750 EUR/m².

There are currently no building documents, the real estate agent will inspect the building file and provide me with the documents. The masonry is two-layered with 24cm inside and clinker outside. Parts of it are apparently already from 1960, then extended in 1980 and renovated in 2001. Bedroom windows are from 1980, the rest from 2001 and 2006.

If I tear the thing down, I would have to pay at least 400K for a new build (160-180 sqm, good equipment), if I follow the prices here.

The development plan allows single-storey construction, otherwise there are no restrictions. So a staggered floor should be possible. The neighboring houses all have an attic as well.

The financing is not really the problem ... (equity > 500 T)

I also don't think the seller will go much lower, I just wonder who would pay that much for such a house....
The house is certainly not a wreck. The condition is very well maintained and high quality, you could move in like this and live well in it with small renovations. We just don't like the style (80s) at all.
But by now I also think that maybe it doesn't make sense.

The alternative is to find a plot of land ... I just haven't seen any under 550T for a long time, then building on top of that with all the extras comes to about 1 million. That's actually too much for me ...

The house is certainly not junk. The condition is very well maintained and high quality, you could move in as is and live well with minor renovations. We just don't like the style (80s) at all.