I have to admit I did not expect the difference to be that great, mostly because I always thought their wage bill is in the same ball park as ours. After checking some reliable sources (telegraph, guardian), their wage bill is somewhere between 100 and 110 Mil. pounds, so at least 120 Mil.€.
With that in mind I have a hard time believing their top earner only gets around 5 Mil.€. I expect that this figure is just the base salary and their contracts to have significant perfomance based bonus payments, boosting the salary in successful seasons by a couple of millions.
The only other possibility would indicate a flawed wage structure in my eyes, where squad players get overpayed and the key players get little money compeared to clubs of their level. This would also mean that they might run into problems in the near future if they want to keep the team together. Their best players will get offers which easily trump what they get right now.