That and there is some barely legal kid getting paid minimum wage behind the counter selling the stuff.With legalization a LOT of the marijuana products out there have become the equivalent of taking 8% of everclear and adding it to grape juice, to sell for $5k, right next to the bottles of Petrus & $3Chuck.
I always sample product in small amounts. Even if its the same product from the same grower it can vary enough to easily overwhelm you. Uncomfortable experiences last too long as @enough said. It's not just the THC number either. I had a supplier that grew primo stuff, all hybrid. Hit like a Mack Truck too. They had a product that was 12% that I figured couldn't be that bad. WRONG. It was very potent. Without sampling I may have easily had an uncomfortable experience.
The other part? Oils, Edibles, flower and concentrate all behave differently based on how you take them. Even oils - whether absorbed or ingested - totally different. Ingestion means it goes through your liver which converts THC to a more potent version of itself.
Just BTW, if it ever happens again, CBD or black pepper. Chewing or smelling black pepper can reduce the feeling. CBD (only CBD) does the same.