That 6300.240 isn't a regular power supply like you would find on a Lap Top. It's a tri voltage power supply meaning that you can change it from 12 to 18 to 24 volt output by swapping a resistor in the cover. I believe its made by Meanwell but could be wrong. Either way, it's not a cheap low quality power supply A standard 24 volt power supply can be used but that limits the ability to reduce the minimum flow from the Tunze's.
That said, one thing people fail to consider when looking at the pricing is that Tunze is a German company. They don't use cheap Chinese power supplies or and the cost of components in Europe are a bit higher. Especially when they import into Europe then export into the US. I know this because of my experience with Royal Exclusiv as well as from my computer business where we import certain products from Germany as well. . European companies have much higher cost of goods and cost of doing business even regardless of where they source components for their products. Tunze Germany needs to have margin for themselves and their dealer channel as does Tunze USA which is essentially a seperate entity and like Europe, there needs to be decent margin for the North American dealer channel which reflects in the MSRP. So yes, quality power supplies can be found cheaper elsewhere but you may not be getting as good of a quality one or one with the same functionality depending on which Tunze power supply you are replacing. Point being that it's not like Tunze is ripping people off. They are providing quality products as evidenced by those of us who have been running the same Tunze's for over a decade. They also have a high cost than a US company that imports directly from China for example. Amazon, EBay, Jebao etc are great examples of that where we compare prices but the quality often isn't the same nor is the business model that has to sustain multiple tiers of distribution including a European distribution channel.