I think one of the biggest misconceptions in the transfer market is that every player you sign has to be 'world class', even though 'world class' is a very subjective term. Is world class reserved for only players like Ronaldo and Messi? Or does starring for a good team in the top league in the world mean you're 'world class'?
Building a quality squad is easily more important than signing a couple of superstars. I'm not directing this at you JayWalker, but why do you lot think we're top and City are chasing 4th? We have a brilliant squad with fantastic chemistry and a load of players who are more than happy to play their roles and don't expect to start every single game. They have a load of players lots of people would probably consider 'world class' who can't play together. Fergie understands this and it's why he continually disappoints the muppets by not overpaying for players who don't fit in with the squad
Ashley Young may not have the same skill level as an Alexis Sanchez, but close to one third the price, is he really going to offer one third less to the team? I think it's been well established that over the past 4 seasons or so, Young has averaged nearly 10 goals and 15 assists per season for Villa. Nani has almost identical numbers this season and we're crowing about him being Player of the Year. I know you can't compare them directly but regardless of what you think of his abilities, he just keeps producing goals and assists year after year. Park and Giggs are gradually moving more and more towards central roles in the squad (combined with Cleverley returning, why I won't be surprised if we don't sign a midfielder), so we have only Nani and Valencia as natural wingers ahead of the likes of Bebe and Obertan. Young would immediately upgrade our attacking options significantly as far as I'm concerned. With he and Welbeck capable of playing as wing forwards, we'd have a great (all English) forward lineup for a 4-3-3 if that were ever to suit the situation.
Regardless of the situation, I can't see Sanchez being 2-3x more effective for us than Young would be for 1/3-1/2 the price.
This is all perfectly true, but however you want to define players that are generally considered as among the best in their positions in world football, it is rare for a truly great team -- both in terms of the success that they achieve and their philosophy on the pitch, which is as historically important to Manchester United as any other team -- to lack one or two players of that type in each area of the team at least. That's not to say that it's impossible to create a great team that lacks those players, but it is certainly more rare than the alternative.
We currently have a number of those players in defence and attack, but the general consensus is that we lack them right across the midfield (perhaps with the exception of Nani). I think that's important and that it goes along way to explaining the difference between the current side and that of 06-09, particularly in terms of the consistency of performance. And I see absolutely no reason why Manchester United should not aim to reach that kind consistency as often as is possible given our history, status, and resources.
Whether we like it or not, and whether it suits our current 'philosophy', we are in an arms race with the biggest clubs in europe for the best talent. Assuming that our academy is insufficient to entirely supply those needs, we can choose to buy those players when they are 16/17 years old and attempt to integrate them from there, or we can buy them in their early twenties when that potential is more obvious and at a slightly reduced fee, or we can attempt to buy them at their peak when they are at their maximum value.
But however we choose to do it, the evidence quite clearly suggests that, on average, the teams that perform most consistently in the major competitions, and the teams that are widely recognized as being the best at any particular point in time, generally have a number of players in key positions that are rightly thought of as being among the best few players in those positions or in any.
Nothing that I have just said explicitly argues against the rationale for also purchasing players like Ashley Young, of course, and as you have rightly suggested, it is of even greater importance to have a broad, multi-talented, flexible, and experienced squad. But the things that we are discussing are not mutually exclusive, and I would argue that both are extremely important to the chances of creating a team that is consistently successful in all competitions, and also one that lives up to the traditions of a club like Manchester United.
This whole argument effectively hinges on whether you believe that there is an imbalance between the two -- a fantastic squad and the required number of special players in key positions -- within the current squad, that the team could be improved with the purchase of one or two highly talented players in those key positions, and also whether you accept that the current team, while significantly better than most in europe, already, is not quite at the level of either the United team of 06-09, for example, or the Real Madrid and Barcelona teams of the current day. And if you will allow me to speculate just a little, it is also arguable that Man City and Chelsea, both of which have the intention and ability to transform themselves in a short space of time with their unprecendented spending power, could also join that list over the next few years.
If you do broadly accept these things, and if you believe that Manchester United should aim to compete with the very best in europe, both in terms of success on the pitch and how that success is achieved, then that improvement obviously has to come from somewhere. While this season could well end as one of the most successful in our history, the performances over the last two seasons will probably not be remembered in the same way. In my opinion, Ashley Young would certainly enhance our chances of repeating the potential successes of this season, but I am far less confident that he would have the same influence on the way in which it will have been achieved.