There are offers whs60, melke smart, kbe gut 58. The price seems to be the same, as I understand it. Which one should I choose? Should they really have the same price or will the price be added up with the cost of work and materials?
It is unlikely that you will choose your car according to the type of steel of which its body is made. So why are you guided by the principle I mentioned? Any window consists not only of frame elements (profiles, elements connecting them), but also of locking elements (fittings) and (not) transparent inserts (glass and/or glass units).
If the fittings and insulating glass in all variants are the same in characteristics, and the same level as the mentioned profile systems, then for myself, I would look at something better.
Rarely, who bundles products from cheap professional systems with good fittings and other quality materials. As a rule, a set is chosen for the sake of price.
And then it all depends on the conditions of the apartment (for example, for renting) and the region.