Oh it's been a while. Nice.
Im sorry but its really funny and out of character to just walk into a store for the first time and just say out loud "Why is everything so expensive and bad quality?" to the owner. Might as well just start throwing hands before saying anything at that point.
It's definitely an odd thing to do, especially since he shouldn't have much context regarding the proper prices for the potions. He does have some context for the prices of the ingredients by now though and he should be aware that the skill to make these potions isn't widespread since this is literally the only alchemist around (well there's another one in the periphery of the town with a shop that's usually invisible and is know for driving out customers so that's not much of an alternative.) I guess it's possible he appraised the potion and then also considered their prices compared to what he's been making in the adventurer's guild and since he's fairly successful, finding the potions to be difficult to afford does lead to some questions. Everyone else is complaining about the prices too.
I think it can also make sense to ask why a product is more expensive to learn of the circumstances that lead to that, as there may be a bottleneck in the supply chain and this guy is literally a material collector.
As for the bad quality, I'm not sure that's what he meant. The other adventurers were mentioning that they were buying low grade potions so it might be that the alchemist is only putting those on display.
But yeah, it's probably just a case of "this fat alchemist is greedy, let's make it extra obvious".