I think that this is not a problem.People which have bigger amount of merit have more chance to get more merits,that is true but main reason is because they make high quality posts so If you have 400-500 merit or even more there is more chance that you will get merit because people see that this guy with so much merit is somebody who have good enought writing skills.There is a lot of people also which gives merit only for high quality post so it depends on each person but most times you will get merit even if you are not in top 200 merit receivers.