Learn English – comma before “and soon” at the end of a sentence

Either is ok. Commas indicate a pause. If you want to emphasize the contrast between the two clauses more, add the comma.

By the way you don't need the "to me" in that sentence; it's implied by the fact that the sentence is written in the first person ("I" is the subject).

I like your car, but it seems too expensive for you.

Advice from the BBC:

A comma (,) generally indicates pauses in speech. But, when it joins two clauses, it indicates a contrast between two ideas. In speech it is normal to draw attention to this contrast by a slight pause. A comma is the usual way of indicating this, although it is not obligatory:

Sheila can eat anything and large quantities of it, but she never puts on weight.

I'm going to make some New Year resolutions, but I don't suppose I'll keep them

The truth about commas is that all the rules are just guidelines to help structure your sentences for readability. The purpose of the comma is to simulate the pause that would appear in the sentence if spoken. It's never required but it often helps.

In this case the comma is most frequently used because a speaker would pause before "although" to indicate a change in the direction of the sentence. For example:

I really love a good steak, but my doctor says I have to cut back on eating red meat.

In a similar way, a speaker would pause to separate the things in a list:

Is there anything in the world better than good wine, good friends, and good conversation?

Anyway, the rule you quote is a nice starting guide, but I wouldn't take it as gospel.