Mechanicorp’s newest product costs so little to make that it appears

You are correct, the above question is a "must-be-true," question, or an Inference question. It is NOT a Strengthener.

How to tell the difference? Many GMAT test-takers are confused on this because they focus on the word "support" in the question stem. Here are the two question stems to differentiate between:

i. The statements above, if true, support which of the following?
ii. Which of the following, if true, supports the argument above?

Now, the big clue in how I worded it is that only (ii) refers to an Argument. And that's the biggest difference for you to be aware of, too: Strengtheners are always about Arguments, and the answer will hinge upon correctly identifying the Conclusion and Evidence and deducing the Assumption from that. Inference questions, such as (i), may not refer to an Argument at all and may simply be based upon a set of Statements, that is, Evidence without a Conclusion, from which you must make a "must-be-true" deduction.

However, it's also worth noting the difference in word order that has logical significance. In (i), the Inference question, we're assuming that that STIMULUS is true -- we would never do this in a Strengthener question, as we're trying to strengthen an otherwise-specious Argument -- and using it to examine the ANSWERS, only one of which "must be true." In (ii), the Strengthener question, we're assuming the ANSWERS are all true, and seeing how each of them affects the STIMULUS differently.

So, to put it really simply: Inference or "must-be-true" questions will look like (i) above: they work down, with the Stimulus taken as true and used to affect the Answer Choices. Strengtheners, which refer to Arguments, take the form of (ii) above: they work up, so that you take the Answer Choices as true and apply to them to the Stimulus in question.

Hope that helps!