Heating and Sanitary Offers Assessment

I can only give my two cents on controlled residential ventilation. If possible, change from flat to round duct. Flat in your offer 20m for 200€, privately or craftsmen get about 50m for roughly 100-120€. You or the craftsman can save money by choosing round ducts.

For example, 1000€ flat to 200€ if round duct.

Had the same scenario where I could have gotten the AlphaInno heat pump myself for 3000€ cheaper online and the heating engineer pockets the 3000€ subsidy. BUT what can you do if you can't/shouldn't install something like that yourself? You always have to weigh how far the "stinginess is cool" motto should go.

the material ...
I quickly and easily found several companies on the internet where the prices are 25 percent cheaper for me as a private end customer.

when I need spare parts for the car, I often get them offline from reputable parts dealers up to 50% cheaper than at the authorized workshop

however, you should be able to install them yourself, most workshops do not like it when you bring your own parts ...

Example Metro, where every normal consumer can notice it.

Believe me, Metro or the grocery retail sector has little in common with the sanitary industry in terms of structure, which is why the example does not fit here. All wholesalers can match internet prices, but the installer is still sitting between them and you. (Sometimes they don't even talk to you if the installer hasn't explicitly "allowed" them to.) That he— as shown here— gets paid for installing does not prevent him from adding a hefty margin to the material again— although there are good and bad ones. Our installer— whom I count among the good ones— sells you the material at the list price, but it is then all-in, so finished installed and usable.

Our installer - whom I count among the good ones - sells you the material at list price, but it is then all-in, meaning fully installed and ready to use

We were also in the same range.
Catalog price e.g. €300 during sampling.
Minus discounts from the plumber, plus installation = again about €300.

PS:
I just thought of an even more extreme example (in the automotive sector)

I had a leaking line in the clutch hydraulics on a Nissan

the replacement part would have cost 60 € at the Nissan dealership

I measured the old part ...
--> I found an identical hydraulic hose (same length, same diameter, same threads) as a replacement part for the brake system of some motorcycle for 12 €

80% cheaper or 400% dealer workshop surcharge I find intense!

25% on the other hand is okay...

I also don’t have a separate installation charge (unless you count the "Baustelleneinrichtung" which, for a heating/plumbing specialist, is not very extensive and definitely not just a one-time cost). The material costs are higher than online prices, but installation and warranty are also included in those.