Cabaye and Clasie both would replace Mason as all-around midfielders capable of creative forward passing, good tackling, and in Cabaye's case, he would've given us a player with lots of high level experience and end product (excellent set piece taker). Let's see how they do at Southampton and Palace this season and we can revisit this debate.
As for Suarez, he is a far better, more accomplished player than Stambouli. A better tackler, a better reader of the game, a better passer of the ball, and lots of top level experience having played a huge role in winning the La Liga title and being one of the unsung stalwarts that helped them nearly win the CL.
As for Ayew, he has far more pace than Chadli and presses the ball better than Chadli. He has way more end product than Andros Townsend (2 goals and 1 assists from open play in the last 2 seasons combined), so having added him to Eriksen/Lamela/Chadli would've given us options across 4 competitions and in the event of injury. But again, he'll be at Swansea, so we can assess this debate again during the season.
Konoplyanka ended up at Sevilla. They've won the Europa League the last two seasons and have been one of the shrewdest operating clubs in the transfer market in the last 3 years. Don't think that's evidence of some type of red flag surrounding Konoplyanka, but instead speaks to the fact that they see him as someone who can help them compete in the CL and become a top 4 team again in La Liga.
Now, to address your points: firstly, there isn't much doubt that we were in the market for the players that I mentioned. I make that claim because the managers we've sacked have all confirmed that these were the players they wanted to sign, only to be offered their cheaper replacements (
That we are after that calibre of player is not in question: that we routinely end up with their less able, cheaper replacements is the problem. Why that happens is the question, especially when we are the lowest net spenders in the Premier League over the last few seasons and definitely have the financial wherewithal to push the boat out for 'extraneous value' players at key times: not always, but at ciritical moments, like when a new manager needs that one player to implement his system (Schneiderlin for Poch, Moutinho for AVB) or we're on the verge of something big (3rd in January 2012). I'd suggest that we routinely fail at doing this because our chairman isn't the type to take even the smallest risk in pursuit of the club's on-pitch ambitions, and completely ignores the manager's valuations of transfer targets in favour of both his own and the scouting team's valuations of those players. The same thing can be seen with the stadium: we are going the lowest-risk route to fund it, and have delayed incessantly (including during that kerfuffle with Archway) to avoid spending any more than we absolutely have to. And while that approach may or may not be beneficial for a stadium project, it is definitely detrimental to the football team, imo. And yes, buying the wrong player at the wrong time can completely change performances as well: sadly, we learned that when we bought Saha and Nelsen in a window where many (possibly even the players) expected real reinforcements to push for the title. We ended up going into a tailspin, and Saha and Nelsen did little to arrest that tailspin.