They didn't say per PC. 1500gp at 5th level is to unusual.
I don't sell potions in those quantities usually they find a few or buy a small number.
Even assuming 7-8 potions per person is a pretty ridiculous amount at that level. That's 350-400 GP
per person just on healing potions, with the expectation of blowing a
further 100-200
per character, minimum, every time you return to town. (For comparison, based on the average treasure results 5e recommends at various levels, this would mean every PC blows 2/3 of
all the wealth they've ever had on healing potions at 5th level...and then consistently continues pouring out at least the same absolute amount almost every time they go back to town.)
Further, each potion only restores 2d4+2 HP, meaning an average of 7. At 5th level, the typical character has 5d8 hit dice and probably a +1 or +2 Con mod (I will err on the lower side, as that is more favorable to the "PCs have tons of healing potions" argument). Using static numbers, that's 9 (=8+1) from first level and 24 (=(5+1)x4) from levelling up, for a total of 33 HP. A single full heal requires more than half of those potions (five out of eight if we're being generous).
Even if we make very generous assumptions that this party is really good at ending combats really fast, they fight very few encounters (only 5) per adventuring day,
and they fight consistently lower-than-party-level CR monsters with weak damage,
AND we assume that the party never ever wastes even a single point of healing (zero inefficiency), this doesn't work out. Assume 8 healing potions per person for a four-person 5th level party, so 32 potions, for an expected output of 224 HP, vs rough approximate party HP of 132 (this is favoring the healing potion argument: if I assume Fighter-like HP and high Con mods, the healing potions are comparatively worse). So even with spending 1600 GP on healing potions, the party can
at best heal about 1.5x their total hit points. Hit dice add in a further (6x5x4) = 120 average per day (it should actually be closer to 110, but I will pretend that hit dice yield above-average results.)
Now, how about those monsters? We'll assume they take on three fights against a single CR3 enemy (quite weak compared to this party) and two fights against a single CR4 enemy (weaker but not quite as much). These fights allow for three enemy turns each. For CR 3, average DPR is 23.5, so a single combat results in ~70 damage, spread across the party; for CR 4, average DPR 29.5, so a single one of these combats results in ~88 damage (both results rounded down). Notice that even
one single fight, of only 3 rounds, against a weaker opponent, still results in the party losing more than half their total HP.
So, we add it up. Hit dice restore ~120 per day. The party takes about 70x3+2x88 = 386 damage taken. I'll reduce that by 10%, since the monster might be inefficient with damage (e.g. damage which takes a target below 0 which is then immediately removed when that target is healed, since healing starts from 0), to a final damage-taken total of 347. So, after hit dice, this party needs about 347-120 = 227 healing. 227/7 (healing required divided by the average healing from a single health potion) = 32.42... But, again, we're assuming perfect efficiency and I have consistently rounded in the "healing potions are enough" camp's favor, so I will do that again here and say it's 32.
Meaning, this party burns through
their entire supply of 32 healing potions in a single day, WITH counting their hit dice healing!
And this was assuming few, fast, easy combats. Even if we were to shorten it to only two enemy-attack-rounds per encounter, we would
still burn through that entire stack of 32 potions before the end of the second day of adventuring.
So, no. I don't accept this argument that healing potions alone are enough, nor that the party is easily able to keep a stock of 30+ potions on hand at essentially all times. The math simply doesn't add up--unless the group is flagrantly, egregiously ignoring nearly all the encounter design expectations of 5e (e.g. having 4 or fewer combats per day, having almost exclusively ridiculously-easy combats, and/or bringing in other sources of healing) AND spending essentially all wealth they've collected up to level 5 on healing potions, and then consistently maintaining or growing that spending every single time they go back to a large town or city thereafter...which they apparently must do on a
very regular basis, as in, at least every other adventuring day.