Honestly when it comes to furniture it is pretty subjective. There isn't a "right amount" to spend on something like a couch because there's so many variables. Do you like the design? Are you happy with the quality and the workmanship? How long do you expect the couch to last before you want to replace it? How much more, or less, could you spend on something of a similar quality/design? Ultimately a couch is going to be one of your more heavily utilized pieces of furniture which to me means I'd spend a bit more to get a quality couch that will last and is comfortable. If it's something you use daily, like a phone, I'd spend whatever I could reasonably afford to buy the quality I needed to not have to replace it every few years.

That said, I understand the "grew up poor" mentality that seemingly plagues us all into adulthood. With your income of lower-mid six figures, the same type of "rational decision-making" (aka penny pinching) you did in your past just doesn't make sense anymore for you. I'm not saying throw caution to the wind with your budget but you can easily afford a $5k couch. Assuming you are applying the same "rational decision-making" to the rest of your purchases you probably have a lot of discretionary cash left over after all your obligations are taken care of come pay day.

A couch is not frivolous so buy the one you like and enjoy the fruits of your labour. You worked hard to get to where you are and you can't take it with you.