Price differences between insulation underlay / aquastop?

Hello everyone,

I am currently looking for a suitable underlay including aquastop for laminate (0.8 cm). Since a build-up height of 1 cm has been agreed with the screed installer, the underlay/aquastop may be about 0.2 cm thick. Now, I have noticed extreme price differences during my research. Are there reasons for this? I took "Bauhaus.Info" as an example. They have, for example:

Dämmunterlage Aqua stopp smart Limited (2mm)
15m²
€26.85
Thermal resistance = 0.057 m² K/W
Water vapor permeability = 100
Impact sound insulation = 20

Dämmunterlage Pro Acoustic (2mm)
5m²
€29.95
Thermal resistance = 0.01 m² K/W
Water vapor permeability = 75
Impact sound insulation = 18

Dämmungsunterlage Expert Aquastop (2mm)
10m²
€4.49
Thermal resistance = 0.038 m² K/W
Water vapor permeability = 75
Impact sound insulation = 19

Dämmungsunterlage XPS light (1.6mm) + Dampfbremsfolie (0.18mm)
20m² and 10m²
€0.99 + €1.29 = €2.28
Thermal resistance = 0.05 m² K/W
Water vapor permeability = 150
Impact sound insulation = 18

If you buy underlay and vapor barrier film separately, you save the most. Of course, you then have to install both. A combined package is still cheap at €4.49. The other combined packages are then significantly more expensive.

Is this justified?

Impact sound insulation, by the way, is only the insulation in the room below you. In an apartment, it is therefore completely irrelevant. The walking noise is relevant for the room itself.

But now the question, why Aquastop or vapor barrier foil?

In my opinion, take the cheapest offer. They all just boil water.