​‎I'm confused about whether "will" is necessary or not.

If you buy a high quality products, you (will) spend more money.

In this case, "will" isn't necessary, is it? I'm confused.
This is talking about future scenario, but "will" isn't necessary.



If I need a car, I will buy a high quality model.
In this case, "will" is necessary because this is talking about future scenario.

Sorry for long sentences. I'm very confused now.

Vedi una traduzione

This is difficult to explain but I will do my best.

When you are talking about an action that always happens, you don’t need “will.”

For example:
A. If I need a car, I buy a high quality model.*
B. If I need a car, I will buy a high quality model.

(A) expresses that EACH TIME you buy a car, you ALWAYS buy a high quality model. Getting a high quality model car is normal and expected for you.

(B) expresses that the NEXT TIME you buy a car, not necessarily always, you will buy a high quality model car. But the time after that, maybe you won’t. (B) doesn’t have a nuance of “this always happens,” it is just a simple statement that expresses what you will do.

“If you buy a high quality products, you (will) spend more money.”
^ In this example, it means basically the same thing with or without (will).

*You can’t use (A) with words that indicate a time, such as tomorrow/next week/etc. You can’t say “If I need a car tomorrow, I buy a high quality model.”