By law no one should give a direct answer. X% is normal, customary or standard violates the Sherman Anti-Trust act. Saying, "you get what you pay for" isn't always the truth either. Some high price agents are lazy, unmotivated and give the industry a bad name. Some discount agents are worth more than what they collect, but not all.
The truth is a great agent is worth more than whatever commission arrangement you make with them. They add value to a transaction and do way more than just post a sign in the yard and have someone make up a flyer. There are lots of strategies on how to market a home, for who, where and what type of marketing may benefit a specific style, location or type of property.
They know how to look out for your safety in both personal ways, property wise and legally. They put your interests above their own and those of the buyer. They know how to read a pre-approval letter and sniff out the ones that mean something versus those that mean nothing. They will negotiate your deal so that you come out as well as possible and leave the other side committed to the deal at the same time.
They will shepherd your deal to a safe closing troubleshooting issues before when possible and as they come up as necessary. They have the vendors, experience and knowledge to keep a deal together when things go sideways, if it's at all possible.
So, what should the percentage be? Whatever it takes, high or low to get the best possible agent to work on your behalf. Your home represents a huge investment, don't take it lightly. A great agent is worth more than whatever you pay them, but a bad one can cost you way more than just a commission. Best of luck.