wp_delete_user - huge overhead in Buddypress?

I am running a Buddypress Website with 8k Users and I want to create a fresh installation as a base for a new project.

I do not want to touch the DB directly because I feel it's dirty and could potentially create conflicts - hence I wanted to clean all users except the administrators just once.

Running wp_delete_user takes ages on a managed cloud server - basically my scripts are timing out after 5minutes with just 300 users deleted. Is it normal that this API function is so expensive? I use it without any reassign option!

Thanks in advance