Is $3,900 to clean and re-stain a small/medium outdoor deck a fair price?

I'm in the process of vetting contractors for a clean and re-stain of our small/medium sized outdoor deck. I'm getting quotes all over the place and don't really know who to trust. Originally I was going to attempt it myself, watched a ton of DIY videos, but figured that would be better left to a professional after reviewing many of the posts here. The deck was built in 2018, is in a high UV/sun area, and the wood has become very gray/faded, but structurally seems sound. I don't think any of the boards need to be replaced. I'm just trying to get it looking good again and protect it from further sun damage. I know this is supposed to be done every few years, and that I've put off the job for too long. Obviously, there's enough of a price difference between the quotes to think twice. This is a high cost of living area. I was originally anticipating a price between $3-4K based on some of the posts here. I'm wondering what others think and if there are any other questions I should be asking. How important is the wood brightener? It's one thing that I noticed the more expensive quote seemed to focus on, and the cheaper quote didn't even mention.