Fashion is inherently arbitrary. This fellow thought he was pretty cool too: File:Thomas Gainsborough - The Blue Boy (The Huntington Library, San Marino L. A.).jpg - Wikipedia
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It’s hot as balls here. Hard to look professional when there is a giant wet line down your pants because you are sweating amounts measured in gallons. Hell, I know a bunch of attorneys who wear flip-flops to work. I may or may not be one of them on occasion.
A sport coat is nothing like a formal (suit or dinner) jacket. Jeans are not pseudo-work pants.
That look, while not my kind of thing, is perfectly reasonable around yacht clubs or other nautical locations.
Unless you are CEO of a tech startup.
Which is not mutually exclusive from “tech startup guy”.
Generally I would disagree with this though. Jeans with a dress shirt and sport coat is an acceptable casual look. Jeans with a t-shirt and sport coat makes you look like you are going clubbing around the Jersey Shore.
I agree with most of what msmith537 mentioned in his post. I am in a somewhat similar situation to you; I don’t use suits most of the time, but need to have them in case of client visits or business trips.
To this end, last year I purchased my first suit in 18 years, which is a navy blue half-canvas suit from Suitsupply.com. This site came highly recommended and is a good compromise between cost and quality. (They also have brick & mortar stores in the US and Europe.) My suit (Napoli model) cost $500, and I had it tailored after receiving it.
I plan on purchasing another, nearly identical suit in advance of a coming business trip in May, and I plan to go with charcoal for the next one.
Huh? Your basic Brooks Brothers Oxford-cloth blue or white button-down goes perfectly well with a suit. Maybe not with those ridiculous “skinny suits” that seem to be in style now, which IMHO make any guy wearing one look like PeeWee Herman, but certainly with a classic two-button suit.
Stand outside of any building in Manhattan housing a bank’s headquarters, or a white-shoe law firm, and observe the men coming out. You’ll see plenty of button-downs.
At least in the United States. The OP is talking about appropriate attire in Europe. I’m not sure about button-downs there – they always seemed distinctly American to me.
Last time I wore a pair of slacks was to a friend’s wedding in August of '08. It’s entirely possible that I will never wear them again.
Don’t mind at all, but I’ll have to disappoint you; I’ve never worked in fashion. I did, however, once work for the stuffiest, most conservative professional-services firm in America (full suits required every day, including Fridays). I picked up a lot of sartorial knowledge there.
It’s the juxtaposition of the casual jeans with the formal suit jacket that makes the look. For example, I would not be kicking him out of bed for combining jeans and suit coat:
Yeah, that jacket with jeans and a t-shirt just looks stupid, and I don’t think the moustache is working either. It looks like he spent and hour on his hair but couldn’t spare five minutes to look for a sensible jacket. 
I hate to sound like Jeeves explaining to Bertie why Prince Edward can wear pink socks with clocks on them and Bertie can’t but really, celebrity (or just general hotness) means such people can flout convention. Some, like Brad Pitt and Keanu Reeves, seemed to delight in seeing how ridiculous they could look and still have people go on about how hot they were.
No more Armani Shoulders. Armani still makes suits but nowadays they don’t look like you’re wearing epaulets underneath.
You don’t have to be a celebrity to flout convention. You just have to be able to pull off the look without appearing ridiculous.
Also, a lot of it depends on context.
Here are some shirts from Brooks Brothers for reference.
Strictly speaking, a button down collar is a more casual look that a spread collar (no buttons in the collar). French cuff shirts (requires cuff links) are least casual and generally do not have a button down collar.
The moustache isn’t my favorite either but it is outshone by the glory of that coat/jeans combo. Rowr. 
Traditionally, a tuxedo is only semi-formal, while tails are formal. And yet, probably the biggest, most public annual formal event in America is the Academy Awards ceremonies, where men wear, at most, tuxedos. (Some come in dark business suits.) So I think a button-down collared shirt with a suit is formal enough for America.
See, to me, so much is wrong with that outfit. Everything from the faux faded/whiskered jeans that are too big, to the jacket that is too formal and loose and the sleeves that have clearly not been tailored (too long). I’d love to see what shoes he’s wearing. I bet they’re sneakers.
But yeah, he’s famous and a good looking dude. Probably no-one gives a damn if he hasn’t showered in days either.
I’m picturing scuffed up black motorcycle boots.
Darn :mad:
Then a button-down collared shirt is more “business casual”.
Trust me. If you are going to wear a suit, you look better with a buttonless spread collar. Button down collars make you look like a guy who put on the nicest casual shirt he has to go with his suit. it’s not like they are more expensive shirts or anything.
I’d go for a white seersucker suit if you are in a tropical/warm climate. Seersuckers look trendy and upscale while being extremely breathable
Not on my salary. This is Nearsucker!
Ask your boss for a raise or run for Congress? Seriously though if you ran for Congress you’d get a good salary, cushy office, almost zero responsibilities and the best healthcare in the country.
Win/Win!
And you’d get featured in fashion magazines like Congressman Aaron Schock (R-IL) and Paul Ryan (R-WI) and Joe Biden (D-DE)