Okay, simple.

First ask to play the cheapest Stagg they have, I'm totally serious.

You'll see how the neck is miles away from the strings. And when you try to bend a note, you'll have that disgusting feeling of "...am I scraping the wood off of the fretboard with the string now?".
The toneknobs will be attached to the bass-guitar, but that's it.
See how much the tone knobs do to effectively change your tone (and I'm talking, try getting a good tone out of it that isn't everything 100% open)
Try the tuners, do they feel sturdy? Probably not. Also, string tension should be pretty sloppy.

And then work your way up. How much every bass plays better and has better options etc.

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