It seems odd to me that A2 actually saves us money for 8 years
This is only true in terms of net salary. The salary becomes more expensive than the current system as of year 7. That's an important distinction because, while the net savings reflects the cumulative impact of the differential in the contracts if you DO sign the player, the year-by-year comparison is what will determine whether those contracts are actually signed. More simply, the fact that I saved an extra $5 last year will have no bearing on whether I'm willing to pay an extra $3 next year.
It's also worth noting that the escalation looks very different for a different base salary. You save money every year for the first 6 if you start with a base salary of $1, sure. But if you start with a base salary higher than $10, you never save money with A2, as compared with the current system. So A2 really emphasizes getting long-term value on players that you identify when they're dirt cheap (which I think a lot of our owners enjoy doing anyway). Once the prices get into the double digits, whether at auction or because the player has been kept a few years already, they quickly outgrow the current system.
Given that the typical rookie age in MLB is 24, that means heralded players would go to auction by age 31 or 32.
I think you're conflating two different population averages here. Typical rookie age is not the same thing as typical rookie age for elite players. Elite players tend to come into the league significantly younger than the average MLB player (e.g. Bryce Harper came up at 19, Trout had a cup of coffee at 19 and then was full-time at 20, Machado had a similar thing at 20/21, etc.).
MLB teams get 6 guaranteed years before a player can first reach free agency, assuming no extension. Under A1, we'd basically have the same system at a very high level. Under A2, there's no similar explicit restriction, but a large proportion of players would price out in that time frame ($27 is a lot, and this is assuming the player started at $1), with a handful going to year 7, but very few going to year 8 ($41). Even if a Trout or Harper-type player gets kept through year 9 ($62), they'd RBL hit free agency around age 30.