Rules:

The suit is only dark blue or dark gray. Black is allowed only at evening events with the black-tie dress code, as well as at funerals and weddings.
The jacket is single-breasted, with two or three buttons. Length — up to the middle of the palm of a freely hanging hand. The fabric is solid, dense, without iridescence (chameleon effect), and gloss.
Trousers of a classic cut, with arrows. The length is up to the middle of the heel with one front fold above the shoe.
The shirt is white, plain, opaque (not transparent), and without pockets. Cuffs with one or two buttons are acceptable, but French cuffs are preferable, with medium-sized cufflinks of laconic shapes. The cuff should peek out from under the jacket by 1-1.5 cm.
The tie without glossy gloss, plain, muted colors (dark red, dark blue, dark gray, graphite). Small geometric patterns or contrasting stripes are acceptable. The tie should not be too wide, and its knot should not be too large. The length should reach the middle of the belt.
The belt is only made of smooth matte leather with a classic laconic buckle. The color of the belt matches the color of the shoes.
Shoes — oxfords or derbies made of smooth matte black leather. Brown shoes are only allowed in the heat. The sole is thin, the heel is 3-5 cm.
Socks up to the middle of the calf, are selected in the color of shoes or trousers. White or multicolored socks are not allowed.

These are generally accepted rules. But some politicians deviate from the rules and add their own corporate identity: Trump wears a bright red tie and printed socks; Putin most likely has higher heels. Macron sometimes wears a turtleneck under the jacket. Canadian leader Trudo wears socks with ducks and star wars. Some civilizations are also wearing traditional costumes, e. g., the Saudi Arabian prince wears a thawb (or dishdasha).

The suits are meaningful. For example, Marcon wears a turtleneck under the jacket if he expects changes from the politician’s decision. The clumsy oversized non-ironed costume can mean that person does not care about the public – Trump is one of them. Obama, at the conference against terrorists, wore a beige suit, that seemed too informal in a context of a speech on such a serious issue. A light suid is only used at weddings and on the beach.

Brands:
Putin wears Brioni and Kiton (4000-8000€). Macron wears a local brand, Jonas et Cie, for just 380€. Biden wore Ralph Lauren at the inauguration. Hart Schaffner Marx and Hickey Freeman produce suits for presidents for 3000-5000€. So, the price of the suit may be any: 400€, 3000€, 8000€ and higher.

Source: RBC.ru