Depay 90k and Martial 65k are not on super high wages yet, and lower than the likes of Ashley Young. Depay chose United because of LVG not money as PSG/City were also interested. Barca and Bayern pay their young players very well the likes of Gotze and Neymar paid high wages and market has inflated further since their transfers. United/Glazers took a lot of criticism for not competing for wages with the likes of Hazard/Silva/Aguero/Toure/Nasri/Moura. Its good that we are adapting now and not losing out to our rivals all the time.
Depay and Martial are MILES away from being compared to Goetze, James or Neymar.
Goetze was one the best CAM's in the world with BVB. James was consistent for a while with Porto, was Monaco's best player, and had an amazing WC. Neymar is Brazil's golden boy, and was practically carrying the team, and lead Santos to the Copa Libertadores, the last player to do so was Pele, btw.
You can't compare Martial & Depay's wages to these guys lol.
However, you could compare wages of Martial to that of Coman, who is playing really well for Bayern. Coman is being paid well less than that. I believe that Dybala, Vietto, Angel Correra, Icardi are also paid less (have to properly check), and they're currently as good if not better than these two.