I've seen mercs and the economy fluctuate a lot in the preview. Because there are several factors at play in terms of what holdings and penalties you have, and how mercs fight in battle, it's a multi-tiered problem.
You guys can't see it in the demo (probably), but the mercenary population is variable depending on your geographical location, which is another important factor. Even if you have piles of cash, if all the mercs are already hired out, you simply can't use them at all. And since mercs have to regenerate their strength over time, they are difficult to abuse in any way after the game passes the 50 year mark (as claims pile up, wars are more frequent). I've seen versions of the game where you end up paying 300 gold for some lousy 1,000 merc regiment because they are all hired and the only one left is only at 25% of its original strength thanks to a recent conflict.
You guys can't see it in the demo (probably), but the mercenary population is variable depending on your geographical location, which is another important factor. Even if you have piles of cash, if all the mercs are already hired out, you simply can't use them at all. And since mercs have to regenerate their strength over time, they are difficult to abuse in any way after the game passes the 50 year mark (as claims pile up, wars are more frequent). I've seen versions of the game where you end up paying 300 gold for some lousy 1,000 merc regiment because they are all hired and the only one left is only at 25% of its original strength thanks to a recent conflict.