How to say "I learned" with comparison between two items grammar

Question

I'm trying to say "I learned that expensive items are not always better than cheap ones."

Should I use the Aのほうが　Bより　(property) grammar to say that?

Also, I don't know the grammar to say "I learned such and such" yet, but I found this other post that says I can use 勉強になりました。

How to say that you "learned a lot" by doing something

So putting it all together I came up with something like いつも高い物のほうがやすい物よりましじゃないを勉強になりました。Is this correct?

Or should i use はずです and say something like this?

高い物のほうがやすい物よりましはずでしたが、いつも事実じゃないを勉強になりました

Answer 1

The grammar choice is fine, but your sentence has a number of errors.

• 勉強になる is an intransitive set phrase which never takes を (although it sometimes takes と). 学ぶ takes an object marked with を, but the part before を must be a noun. You have to nominalize the clause using こと.
• まし is not the right adjective here. See this question for the reason.
• いつも～じゃない is ambiguous, but tends to mean "always not" or "never" rather than "not always/necessarily". Please learn how to use ～とは限らない.

Corrected version:

• 高い物の方が安い物より良いとは限らないことを学びました。
• 高い物が安い物より良いとは限らない、と勉強になりました。
• 高い物の方が安い物より良いと思っていましたが、それが事実とは限らない、と学びました。