Мне подходит этот вариант, потому что он дешевле.

Because the verb подходить in this meaning works with the dative case for the person.

So Russian structures this idea more like:

• This option suits me
• This option works for me

Here, этот вариант is the subject, and мне means to me / for me.

So:

• Я = I
• Мне = to me / for me

That is why Мне подходит этот вариант is correct, not Я подходит...

Here подходит means suits, is suitable, works, or fits.

The verb is подходить. It can have different meanings depending on context, for example:

• подходить к дому = to approach a house
• подходить кому-то = to suit someone

In this sentence, it does not mean physically approaching. It means that this option is appropriate or convenient for the speaker.

So Мне подходит этот вариант is something like:

• This option suits me
• This option works for me

Because этот вариант is the grammatical subject of the sentence.

Russian is built like this here:

• этот вариант = this option
• подходит = suits / works
• мне = for me / to me

So literally, the structure is close to:

• This option suits me

Since этот вариант is the subject, it stays in the nominative case.

Because вариант is a masculine singular noun.

Russian demonstratives must agree with the noun in gender, number, and case.

So:

• этот = masculine singular
• эта = feminine singular
• это = neuter singular
• эти = plural

Since вариант is masculine singular, you need этот вариант.

Because он refers back to вариант.

Since вариант is a masculine noun, the pronoun that replaces it is он.

So:

• вариант = masculine
• он = he / it, masculine

In English we say it is cheaper, but in Russian the pronoun matches grammatical gender, so он дешевле literally looks like he is cheaper, though in meaning it is just it is cheaper.

Because дешевле is the comparative form of дешёвый.

• дешёвый = cheap
• дешевле = cheaper

The sentence is comparing this option with something else, even if that other thing is not stated explicitly.

So:

• Он дешёвый = It is cheap
• Он дешевле = It is cheaper

Russian often uses this short comparative form instead of something like более дешёвый.

Russian often leaves the second part of the comparison unstated when it is obvious from context.

So он дешевле means:

• it’s cheaper
• it’s less expensive

The listener understands that it is cheaper than some other option, plan, product, and so on.

If you want to say the full comparison, you can add чем:

• Он дешевле, чем тот вариант. = It is cheaper than that option.

But in your sentence, the comparison target is simply understood.

Because in Russian, the verb to be is usually omitted in the present tense.

So Russian says:

• Он дешевле = It is cheaper
• Она дома = She is at home
• Я устал = I am tired

Russian does not normally say a present-tense form of быть in sentences like these.

Because потому что introduces a subordinate clause, and in Russian that clause is separated by a comma.

So the structure is:

• main clause: Мне подходит этот вариант
• subordinate clause: потому что он дешевле

That is why the comma is required:

• Мне подходит этот вариант, потому что он дешевле.

Потому что means because.

It introduces the reason for something:

• Мне подходит этот вариант = This option suits me
• потому что он дешевле = because it is cheaper

A very literal breakdown is not always helpful, so it is best to learn потому что as a fixed expression meaning because.

Yes. Russian word order is more flexible than English word order.

Your sentence is completely natural:

• Мне подходит этот вариант, потому что он дешевле.

But you could also say:

• Этот вариант мне подходит, потому что он дешевле.

The basic meaning stays the same. The difference is mostly in emphasis and flow.

For example:

• Мне подходит этот вариант... puts a little more focus on for me
• Этот вариант мне подходит... starts by highlighting this option

This is a very common question.

• нравится = is pleasing / I like
• подходит = suits / is suitable / works for me

So:

• Мне нравится этот вариант = I like this option
• Мне подходит этот вариант = This option suits me / works for me

In your sentence, подходит is better because the reason is practical: он дешевле. The speaker is talking about suitability, not just personal liking.

Because the sentence is describing the option’s suitability right now.

• подходит = suits / is suitable now
• подойдёт = will suit / will be suitable

So:

• Мне подходит этот вариант = This option suits me
• Мне подойдёт этот вариант = This option will suit me / should work for me

Your sentence is about a current judgment, so подходит is the natural choice.