Is 5-10% earnest money excessive?

Hi, my realtor told me that 5% earnest money is standard, and 10% shows you’re serious. We are talking about $500k+ properties. This is an area that has traditionally been hot, but has cooled substantially and listings are now sitting a while. I can’t help but think I’m getting BS’d. I’m a serious buyer with the means of getting it done, but I also don’t love throwing around large sums of money needlessly. I would appreciate any thoughts. Thank you in advance.