6000 SQS requests where I don't have any queues defined

Without looking at your specific account it's difficult to give you a specific answer. You may want to open a billing support case around this question. Could it be that you may have an SQS queue in a different region? I suggest opening Cost Explorer, filtering (right side) on SQS AND under Usage Type by Requests (in my account there were 102 request types). Then Group By (the top) by Region. This should give you a new lower graph with the number of requests and you should be able to see which region has all the requests. You an then verify that the region you are looking at for SQS queues is the one with all the activity.