Use of は in place of の


My question is about this sentence:

我が社の商品は値段を上げません。 (wagasha no shouhin wa nedan wo agemasen)

At first I thought there was a typo ("wagasha wa shouhin no nedan wo agemasen"
or something like "wagasha no shouhin wa nedan ga agarimasen/ageraremasen"),
but I was reassured this is not the case by two 先生 of mine.

That は would actually be a の, but it's changed to は to add emphasis. So it's
not a topic-は, it's more a contrastive-は(?)... or so I thought, because I've
never heard of an emphatic-は (please don't confuse "focus" (集点) with
"emphasis" (強調), which is a different thing).

Moreover, even if the one in the sentence is not a topic-は, I can't have one
at all in this sentence (while I can have a topic-は and as much contrastive-は
as I want). Specifically I've been told I can't put in wareware wa as a topic:
我々は、我が社の商品は値段を上げません。

However it's grammatically correct to think the subject is "wareware ga"...
我が社の商品は我々が値段を上げません。 ...but I won't ever find a sentence like this.

I've studied this topic (は と が) really hard and never came across something
like this. The explanation I've received is seriously lacking: it's more or
less what you can expect of a native speaker (who knows what sounds right, but
can't tell you why) so I ask you. **Is it true that not just が and を can be
replaced by は, but also の?** Can you give me more examples and help me to
reason this out?

Every answer will be very much appreciated




**Disclaimer** : I am not a native speaker; I think my sentences are correct
but they might sound slightly weird.

This is a case where the topical 〜は sets a "domain of discourse", i.e. a
context. The following noun 値段 is _indirectly_ implied to belong to the
context noun 我が社の商品.

This may sound confusing, so here are some simpler examples:

> 日本語は、文法が難しい。
>
> Talking about Japanese, the grammar is hard.

So the exact meaning is slightly different from

> 日本語の文法は難しい
>
> Japanese's grammar is hard.

In the first case, you first establish "OK, we are talking about Japanese
here", then you say, "The grammar is hard". Since we have the overarching
topic of Japanese, we can do things we can't do just with の, for example:

> 日本語は、文法は難しい。でも、発音はとてもやさしい。
>
> Talking about Japanese, the grammar is hard. But the pronunciation is easy!

We can do this because the 日本語は topic or "overarching theme" hasn't expired
yet.

But with の, it means something strange:

> 日本語の文法は難しい。でも、発音はとてもやさしい。
>
> The grammar of Japanese is hard. But pronunciation (as a whole, of all
> languages) is easy!

In this case, the "pronunciation" has no relationship to "Japanese", so it
refers to pronunciation or phonology as a whole, i.e. in general for all
languages.

This also explains the usage of が with あります. Too many people are taught "が
replaces を" which is completely wrong. This usage relies on は's nature:

> 私は本があります。
>
> Talking about me: there's a book (that's mine)

Many other languages have a similar structure, such as Latin:

> Angelis alae sunt.
>
> "To angels, wings exist" = "Angels have wings"
>
> 天使には翼があります。

**TL;DR** : は does not replace の here, it means what は means. Through its
topic-setting nature, it indirectly implies possession in some cases, but also
many other things, such as being able to extend the topic through several
sentences.

