Is an additional charge for high-quality lamps necessary?

Insanity! What an Occhio costs. (but they look incredibly good!) I bought all my lamps from a China-based company. For example, I have 26 outdoor lights in the brickwork, I can't pay €100 per spot. (I paid about $12 each for up&down aluminum spots, powder-coated black with transformer) So, I probably subconsciously tightened the purse strings there. For standard GU10 ceiling recessed spots in the upper floor and the kids' rooms, I simply bought 100 pcs. (€2.50 for socket and bulb) Whoever owns the luxury penthouse in the city center will hardly put Asian lights in the living room. I rather invested in flush-mounted fixtures from brand manufacturers etc.

and what does the homeowner who has no money for planning do? He just has the electrician do something classic in the ceiling, a few spots and that's it?

Well, what else should you do? It works anyway. Even with lamps from Ikea or Amazon. And if the lamps are not particularly eye-catching, no visitor will notice whether they cost 50€ or 500€.

With spots, I can still somewhat understand that good spare part availability is helpful, but with normal ceiling lamps, it really doesn't matter. Tastes change and eventually you will want to replace the lamps anyway.

I snapped them up at Kaufland back then, there were these LED panels with adjustable color temperature in square and elongated rectangular shapes, I think for 30 or 40 EUR each. Compared to the counterparts from the hardware store, which are often not more expensive, they are much less conspicuous (no thick frame) and don't stick out as much (flatter). However, I wouldn't have thought at the time of purchase that it would take over a year for me to install them.

We had these professionally done by a regional dealer. What shocked me were the sometimes insane prices.

The planning was free and is part of this dealer’s service,

… part of the sales service. Even a regional specialist provider makes their mixed calculation.

Now the question is whether the spots for e.g. €100, i.e. the middle range, can be equivalent to those for €250?

I don’t think so. Whether they are worth €250 is another matter, but I am convinced that they are of higher quality than hardware store or Amazon goods.

Do you perhaps have a few brands to stick to? Basically price-performance?

Price/performance is relative. With lamps just as with kitchen appliances: I’m not very familiar with current lamp brands, but for many, comparable performance in kitchen appliances only starts from Neff, Miele, among others. More affordable brands are rejected. For the brand Occhio: if you like it and want to have it, you just have to pay the price. Personally, I find €500 as a light source completely overrated. Not only that: I find them absolutely and totally ugly. Regarding internet prices: one should consider that many online retailers cannot deliver immediately because they have no warehouse. As an end consumer, you are dependent on a few intermediaries, so sometimes you have to wait several months until they tell you that nothing is deliverable anymore. Of course, you have already paid due to prepayment. Many online retailers only exist for a few years, then returns are impossible. Then the comparison with household appliances like Bosch: the production number reveals that special batches are made for the market. If you buy the same device from a specialist dealer, the last number or letter is different and the device is more expensive… one can ask oneself whether some small parts are of lower quality… And last but not least, the low price may be offered by a fake/fraud company. That doesn’t happen so rarely either. In this respect, in my opinion, one has to weigh the purchase on the internet with high prices a bit: not all that glitters is gold.