Student or Learner
1) Product A is cheaper than B
2) Product A is much cheaper than B
Which sentence will make A sounds much more cheap?
If A is "much cheaper" than B, the difference is bigger than simply being "cheaper."
Of course, if B is very expensive, then even if A is "much cheaper" it still may not be "cheap." It's just not as expensive.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.