To be precise, anyone who has ever obtained anything from the Lordaeron's shop is now able to skip the queue. It's not the act of donation that makes you able to skip queue but rather obtaining something from the shop. That is what provides you the perk, not the donation itself.
In reality, you can get anything from the store and it will provide you the perk, anything quite literally.
We also want to elaborate that we are working on raising the cap as high as possible. Our development team has been analyzing performance, deeply going through logs and trying to cut down anything that causes bad performance. We would like to report the current situation to the community, which is that we've been slowly improving performance as we go and with good results so far.
This temporary queue skip feature is a temporary solution we have towards a big long-term problem that we aim to solve. Our realms are meant to be played, not for players to wait in queue. We understand your frustrations and we are genuinely working on improving whatever we can to allow more players. Currently, we've been prioritizing solving any host issues that we have as you could probably notice, we've had a bit of issues with our network in our server racks lately.