Boof's projection and Teng's projection at the time of trade I would rate as similar. Teng could absolutely become much more, and when I did a report on him last summer, I had an MLB comp that was much higher than a 4/5 guy. Berroa is a lottery ticket. Liriano was as well. You could make the argument at the time that Nathan would not have broken through the Giants bullpen and other such arguments made here, but Twins fans view that deal as highway robbery, especially in light of what the team received for giving up those players.
You can have your opinion on Bonser. At the same age as Teng he was the 29th ranked prospect whereas Teng is nowhere to be found. Liriano was coming off an injury season. Prior to that he was a top 100 prospect. To compare Teng to Bonser would then say that Berroa is comparable to Liriano. Your stated opinion seems to be that Teng and Berroa were comparable to 2 players who were ranked as top 100 prospects in all of baseball at some point before their trade.