يختار البعض هذا السعر.

Because البعض is grammatically a singular masculine noun in Arabic, even when it refers to some people.

So Arabic treats it like a singular subject:

• يختار البعض = literally, the some chooses
• natural English: some choose or some people choose

That is why the verb is يختار and not يختارون.

البعض means some, some people, or some of them, depending on context.

A useful distinction is:

• بعض = some of ... and usually expects something after it
  
  • بعض الناس = some people
• البعض = some / some people / some of them as a more complete standalone expression

So in this sentence, البعض works by itself and means something like some people.

Because this is a very common Arabic sentence pattern: verb + subject + object.

Here the structure is:

• يختار = verb
• البعض = subject
• هذا السعر = object

So the sentence is a normal verbal sentence in Arabic.

You could also say:

• البعض يختار هذا السعر

That version is also correct, but it gives a little more emphasis to البعض as the topic.

يختار is the present tense of اختار, meaning to choose.

• past: اختار
• present: يختار

Its root is خ ي ر.
This verb is a derived form, not the basic Form I pattern.

For a learner, the most useful thing is simply to remember:

• اختار = chose
• يختار = chooses / is choosing

It is pronounced approximately:

yakhtāru

A few pronunciation notes:

• يـ = ya
• خ is the throaty kh sound, like in German Bach or Scottish loch
• ـتار has a long ā sound

A rough stress pattern is:

• yakh-TAA-ru

In normal pausal pronunciation at the end of a sentence, you may hear it more like yakhtār.

Because اختار / يختار is a transitive verb: it takes a direct object.

So Arabic says:

• يختار هذا السعر = he chooses this price

No preposition like to or for is needed.

This is similar to English choose something.

In standard Arabic, the normal order with a demonstrative is:

• هذا + noun
• هذه + noun

So:

• هذا السعر = this price
• هذا الكتاب = this book

That is the standard MSA pattern.
The noun after the demonstrative is definite, so it normally has الـ:

• هذا السعر
• not هذا سعر

If fully vocalized, the sentence is:

يختارُ البعضُ هذا السعرَ

Here is why:

• يختارُ: present tense verb in the indicative
• البعضُ: subject, so it is nominative
• هذا السعرَ: direct object phrase, so it is accusative

A small detail:

• هذا itself does not show the case ending clearly in the same way a regular noun does
• the noun السعرَ shows the accusative ending

In everyday unvowelled writing, these endings are usually not written.

Because it is part of the phrase هذا السعر = this price.

In Arabic, when a noun follows a demonstrative like هذا or هذه, the noun is normally definite, so it usually takes الـ.

Compare:

• هذا السعر = this price
• هذه السيارة = this car

So the definiteness is required by the demonstrative structure.

Not always. السعر can mean:

• price
• rate
• fare
• charge

The exact meaning depends on context.

For example:

• in a shop: price
• in finance or exchange: rate
• in transportation: fare

So in this sentence, the best meaning depends on the larger context, even though price is often the default choice.