Is it common for Saudi Arabian men to wear "western" clothes?

the only thing making sense is your last sentence. strange first post.

More and more young Saudis are wearing western cloth, but it does not mean that they had abandoned the traditional dress (Thoubs) . Thoubs are still largely worn in family and social occasions, going to school and on daily basis as a matter of fact.

You will see more Saudis wearing Western Cloths in large cities specially Jeddah and less in smaller cities.
A Saudi, by law, will be denied access to official government office if he is not wearing a thoub.

There are famous Thoub designers that people follow, Lomar Thoubs by Loai Naseem and his wife ( The D&G of Toubs) , Yahya Bishri (The Versace of the thoubs) and Thoby by hatem Alakeel( the Armany of the thoubs) to name few …

You can buy thoubs starting from SR60-3000 (and even more if you want to go over the top)

It’s not a boring question after all !! 

Saudi men have fashion sense. They even get the high end brands. Most of them are into such.

I've never seen a proper Saudi (this includes the Yemeni who've been here all their lives) not wearing traditional clothing at work - and only 25% or so wearing "western clothing" outside work. But bear in mind in some cases there is an extra incentive payment to dress properly for work.

I mean let's be honest if you could wear the same thing every day without worry why wouldn't you. Just choosing the tie and cufflink set is too much hassle for me.

strange post indeed. the oil boom opened the conservative market with western type fashions. french fashion houses are designing and selling Arabic clothes and accessories. Ask Lagerfeld.

Thoub is immensely worn by the Arab people the fact that it's part of their norms/customs. Not only in Saudi Arabia but like Bahrain, UAE, Oman, Kuwait and Qatar just to name a few, and you can distinguish the Arab nationality on it's distinctive detail whether the head dress or Thoub itself (slippers as well).

The evolution of Thoub from classic white crisps cotton/silk comes into fashion with a twists adding some flare to color blocking and embroidered details depends the person how eclectic he is.

All brands from High end to High street like Armani, Gucci, D&G, Diesel, Sonia Rykiel, DVF, MJ, Zara, H&M, Gap, Forever 21, Topshop and Topman et. al. are largely worn here in Saudi Arabia. Saudi people spends money in shopping, especially the young generations are now into fashion forward scene and jumping into the bandwagon of trend-setting.

Did you know that one of the Forbes richest people lives here in Saudi Arabia, we don't know maybe he is one who has the large shares of stock in the world's famous fashion brands like LVMH /House of Dior and Chanel.

the men look fine in their thoubes, very fine, indeed. --- but the brands are (hardly) worn by men and generally worn by women under their abaya.

back to those thoubes. FINE.

I've never seen a proper Saudi (this includes the Yemeni who've been here all their lives) not wearing traditional clothing at work - and only 25% or so wearing "western clothing" outside work.

You need to come over to Jeddah, lots of Saudi's wear western clothes in work, and they are even more casual hanging out by the beach.
I have Saudi friends who don't even own throbes!