I once had fake honey in my home and I get to observe it side by side with pure honey.

Not really fake la, but my mom believes that the fake one was honey adulterated with sugar water.

After storing them for like 3 months later, the pure honey crystallized and has white residue at the bottom of the jar. Fake one doesn't.

I had those before, those were really delicious man. And yea they are usually that expensive, I'd suggest you try all the reputable brands because their texture and taste does not differ much from brand to brand. Manuka honey has a complex taste profile and texture to it you just know if it's fking Manuka honey when you taste them, can't escape.

Chances are that you might be having adulterated Manuka honey, because nobody can fake it's taste other than diluting it with sugar syrup.