If you need to point out the watch and explain its value, you've already lost.

"Well, the jerk store called, and they're running out of you!"

You see this? This is called a "smart phone." Not only will this tell me the time like your watch, but it can also do a bunch of other things. I can look at pictures of raccoons wearing silly hats or I can use it to insult someone on the other side of the planet. It also cost a fraction of what your watch cost. I'm sorry to tell you this, but I think it should go and get your money back. It sounds like you've been scammed. As a matter of fact, let me give you my friend's phone number. He's an accountant, and I think he'll be able to help stop you from making stupid purchases in the future.

Does 0 to 60 in ONE minute! It's garbage.

And it tells the same time as a $5 Casio, but it's heavy and gaudy. I guess money can't buy taste.

"I don't have the habit of looking at other people's watches. Thanks for pointing it out, I guess, I might have otherwise missed that detail entirely."

(Biz-bro mind cannot comprehend this)

The statement is to set them apart from from you and to display power. So you could go with something like,

"Shit, they still make you buy your uniform when you rich eh. Some things never change."

But more elegantly. Reassert that they are subject to others' power/approval and relate to them to assert that they're no different from you.

"Wow, you're really shit at bargaining. They really took you for a ride!"

You paid that much for a watch that looks like you steal from your grandad?

laughs gently and sighs

"This is a six ounce cup of bath water from a YouTube influencer..."

"It's not my fault you're stupid"

"Didn't ask"

get really really enthusiastically interested in the watch. ask for details seem super impressed. massage that wealthy ego to the point of basically a blow job. but then just like keep going. see how long you can keep the topic on that one specific watch. don't ever let him talk about anything that the watch means or about the dynamic he tried to establish.

optionally, loose interest and leave without ever having let anything be said that wasn't about the watch. this is how you weaponize autism against egotists.

"I wouldn't want to paint a target on my back like that. Did you hear about Chesterwick's son getting kidnapped while backpacking in Burma?"

Man, it is a shame you can't buy class because you could use some.

good, maybe you can sell it to buy some human decency then

"mine was 5 bucks at goodwill, sounds like you got scammed, sorry"

I'd just start laughing and point at them.

That's quiet an expensive way to look cheap

“I don’t mean to victim blame, but I try not to look like I’m worth mugging.”

I wouldn't even hide that watch up my ass.

So you are fiscally irresponsible and you are proud of it? Good to know…

"Yes, your fancy jewelry is very pretty. Good job."

Edit: after I stopped laughing, of course.

I can afford not to have a watch.

don't. make a "oh poor guy" face and move on. he wants you to engage, to be angry, if you don't he will be mad

What is it for?

A lot of replies here still wander into sounding mad imo Instead, I would fake not getting the insult and just make them uncomfortable by saying something like "Wow that's cool :D" and then just move on. Sort of like when you acknowledge a child doing something dumb but they're so proud of it you don't want to ruin it for them.

Quite a low bar considering that I don't need a car of my own.

Will your regular charge you half price when she doesn't see you wearing it?