In order for ANet to fix the swim-speed infusion problem is to literally remove swim-speed infusions +10 to +14. Have +15 be the base number you get from the chests instead. This reduces the cost down to around 7.5k gold for a +30 which is way more reasonable.
5:28 Don't forget that materials will adjust in price per week based on which map is most profitable. So during the week that is most profitable, the materials usually drop in price from people spending their PSMM. So if you grab the materials and wait a few weeks, the price of those materials could go back up before that map is back in rotation.