Jian You Tai Xu
I feel like he is undervalueing the price of those fish. Those pellets mentioned before probably have worse effects and cost 5k~ each and I wouldn't be surprised if you can't take them too often as they might leave some impurities in your body. While the fish seem to actually cleanse the body of impurities and give immediate effects. If I was able to buy those fish I would probably long for it even if it costs 50-100k each. I probably wouldn't be able to afford it though, but I would still wish I had that money.
so, when he comes back to the school? cult? sect? he will take the challenge he issued to the inner disiple, time is relative in chinese novels, he spend 6 months with his friend, cultivate a couple months and then stumbles upon a treasure trove and spend a few more months there training, ****ting alot and eating. He will be just in time, they will only be able to talk down on the MC for about one chapter before he arrives just in time for his 2 month appointment.