How do you assess the burglary resistance of the following windows?

What do the locking lugs look like? How many mm are they worn down? Older windows show lugs that are worn down only halfway, so they only move halfway into the lock. The further the lug moves into the lock, the more leverage is required. Best regards in brief

And then you probably only have RC2N

In your place, I would install additional locks instead of mushroom heads. That is cheaper but possibly equivalent in terms of protection.

What exactly do you mean by such additional locks? Lock on the handle? But that wouldn’t change the possibility of relatively easy prying, would it?

Caspar: No, not yet any further offers. 300 euros per sash seems very expensive to me too; we definitely need to get more offers. But if it really is THAT expensive, in my opinion these upgrades are hardly worth it, and new windows would be a better option in comparison. Although we definitely cannot replace all windows at once now, but investing a few thousand in old windows, hmm.

Yvonne: I have not measured these locking noses, I have to do that sometime!

The further the nose moves into the latch, the more leverage is required

With a normal lock, will that really help? It takes 4 instead of 3 seconds? Lifting over is lifting over, so it should hardly matter how far they slide into the "latch".

Mizit, use your favorite search engine and look up "Stangenschloss"

Locks in the handles cannot and should not be a protection against prying open, but an addition: securing only the closed window against prying open, but not the tilted window against full opening, would be only half a solution. A balcony door can be quietly "extended" to the handle lever with a glass cutter to prevent reaching through; kicking in makes the noise the burglar wants to avoid. The time for the burglar runs out from the moment he is noticed.

Per sash, the replacement should remain in the double-digit range; for labor, I would estimate half an hour. I cannot give exact prices; only that it is still very much in demand for aluminum, even for older windows. For plastic, your windows are still in very good condition. So in my opinion, it would be a worthwhile operation.

Using a glass cutter on a balcony door to "extend" an opening to the handle lever is quiet

And takes far too long with triple glazing

The replacement per sash should stay in the double-digit range

That is the price in new construction, or with new windows. A simple Google search shows prices of at least €150 per sash.