There's a huge difference between AWB and Martial and Rashford, and I do agree the latter 2 are indeed proving to be overrated. However they play up front for Manchester United, AWB plays defense for a garbage relegation battling side, not hard to stand out when the sole remit of your job is to destroy, it is much harder to create and score for the biggest team in the country that is never out of the spotlight, there are vast differences in the levels of pressure and scrutiny in regards to the jobs these respective players are tasked with.
You listed some young players doing well, I don't count Sterling as her's older, but look at the top class experience around which those young players are thriving, I mean Sane plays with Aguero, De Bruyne and Bernardo Silva, Dele plays with Kane, Eriksen and Son, TAA has van Dijk and Fabinho protecting him defensively and in front of him he has a world class forward in Salah. You mention the class of '92, when they came into the fold they had Schmeichel, Pallister, Bruce, Irwin, Keane and Cantona to carry the burden of the club while they settled in. Now look at our current team, we have no leaders or personalities or world class players to shoulder the team for the youth we have, nevermind adding more.
As for the price, in an ideal world it wouldn't matter, but we aren't Real are Barca, clubs who ran for the glory of winning trophies. We are ran by businessmen who care about top 4 CL money and nothing else, so we have a budget, hence when Barca lost Neymar they went and spent north of £300M on Dembele, Coutinho and Arthur, we lost Ronaldo and bought Valencia and got a broken Michael Owen on a free, we just got away with it because we had the greatest manager of all time.