Why are there no Sarmatian invasions during EB's period?

[Jolt]

Can't they grow anything in those places? Like teas in some mountainous regions in China?? I'd be surprised if there is any land on earth that can grow grass but nothing else.

Growing? Yes, they can, with sufficient labour and hardwork, grow many things in hostile soils (Bad weather, rocky soil, having to dig deep and keep revolving the lands). But as I said, it takes too much time and labour, without sufficient guarantees of a successful harvest, how small it may be, if one at all. But I do recall asking for an example. Tea wasn't grown in Europe, nor was in Persia at those times. Furthermore, tea wasn't very valued in the Chinese society at the time of the game, thus was not a lucrative product, and thus wouldn't spread through commercial trade.
EDIT: As for your very first question. Lusitanians, for instance did use mountainous oaks to collect acorn. They in turn used these to make acorn bread. But they didn't grow them as far as I'm aware.

Like Romans, of course :)

Alexander payed for nomads in his campaign in Bactria. Did the Macedonians citizens suddenly began feeling their economic power diminished? Did they suddenly began getting greatly overtaxed? How many even knew that he hired nomads?

It's the same thing. As I wrote in previous post, anyone in a socity who is not doing productive works represents a cost to this entire socity.

You could argue that they wouldn't do anything else, well then why not just remove them and replace the army of nobles with levy or professional soldiers?

Did the Macedonian economy cripple down because many Macedonian noblemen left Macedonia with Alexander when he went to fight the Achaemenids? Nope. Things aren't as interconnected as in the modern world, mate.

Because levy or professional soldiers (Or 99% of them, at least. Those who would be rich to afford such things wouldn't certainly be risking their lives for someone else) can't afford good quality mount, heavy armor (Both man and horse), weapons (spear, sword, bow, quiver, arrows), shield, etc. Btw, what do you mean by professional soldiers? Mercenaries? If so, then read the first parentesis of this paragraph. The professional soldiers are the noblemen.

[Vorian]

Alexander payed for nomads in his campaign in Bactria. Did the Macedonians citizens suddenly began feeling their economic power diminished? Did they suddenly began getting greatly overtaxed? How many even knew that he hired nomads?

Alexander had previously seized the treasures of Persepolis which were more than enough to fund any war.

Did the Macedonian economy cripple down because many Macedonian noblemen left Macedonia with Alexander when he went to fight the Achaemenids? Nope. Things aren't as interconnected as in the modern world, mate.

Actually yes. Macedonia was really poor and undermanned in the following years. They barely defeated the revolted Greek cities in the Lamia war and the kingdom stopped playing a big part in the Diadochoi wars quickly. Pyrrhus almost conquered the damn place!

[Jolt]

Alexander had previously seized the treasures of Persepolis which were more than enough to fund any war.

The point being that treasuries normally have funds alocated for war, which do not come from taxing the people.
EDIT: Actually, most of the wealth would come from takign the Persian treasury after Issus, I think.

Actually yes. Macedonia was really poor and undermanned in the following years. They barely defeated the revolted Greek cities in the Lamia war and the kingdom stopped playing a big part in the Diadochoi wars quickly. Pyrrhus almost conquered the damn place!

Actually no, in the timeline I'm speaking. Imagining that they all didn't die in Alexander's campaigns (Imagining he took Darius's offer to settle the border by the Euphrates, returning with very few casualties) and many returned home, there wouldn't be the "instant cost of productivity" he speaks about. Also, Macedonia wasn't very populous in the first place, which would explain why it went kaput in terms of manpower after Alexander.

[Vorian]

Actually, most of the wealth would come from takign the Persian treasury after Issus, I think.

No it's Persepolis. Can you imagine Darius carrying all these mountains of gold around? In Issus he just captured his personal buggage.

There was a series of small but ingenious battles at the Persian straits when Alexander with a small mobile force tried to force his way to Persepolis in order to be the first that gets the immense treasure it held. It's too bad that it's not famour like his major battles since it really shows his strategic abilities.

[Jolt]

No it's Persepolis. Can you imagine Darius carrying all these mountains of gold around? In Issus he just captured his personal buggage.

There was a series of small but ingenious battles at the Persian straits when Alexander with a small mobile force tried to force his way to Persepolis in order to be the first that gets the immense treasure it held. It's too bad that it's not famour like his major battles since it really shows his strategic abilities.

Indeed, I stand corrected. Checking my sources, Alexander took around 55 tons from Issus and 2,500 from Persepolis. It also explains all the more why even if Persia would be invaded, one could afford the luxury of buying armies without overtaxing the common population.