this is what I think. arteta is your best player by some distance.
pienaar is certainly a good player, technically very correct and very willing, but there are plenty of wingers-cum-attacking midfields who are primarily dribblers and do a bit of passing on the side. he has a lot of strengths but doesn't stand out at the higher levels.
arteta on the other hand is a bona-fide playmaker, one of the most accurate passers in the premiership and one of the most intelligent. he's very slow for a wide player, however, and he's short. he seems to lacks the ability to work as effectively in the centre of the park.
alonso is much taller and stronger, has a greater range of pass. he certainly has the knack of playing quarter-back, which makes him the most desirable sort of midfielder in the modern game. both he and arteta have great work rates and play very intelligently, but even so, alonso is/was more influential in the difficult position, and so is more valuable than arteta. the other factor is that arteta is not on mega-bucks and his contract is running down.
because of all of this, as much as I think he could be just what city need, I cannot see a situation where the price would over 18-21m. as someone else has said, hughes is long gone, we are unlikely to put everything into pursuing one player when there are alternatives... gourcuff for one has more flair and possibly even better passing, even if he suffers from the same lack of pace as arteta, as a much younger player he will fetch 20-28m.