What some distributors do not tell you is that gaskets themselves and the plates are very expensive.
And if you dismantle the plates, when you mount them back, then invariably you will have to replace all the gaskets. Their price can reach 50% to 100% of the price for a new brazed plate heat exchanger.
The heat transfer for gasket heat exchangers is lesser then in the case of brazed ones. This means that brazed heat exchangers need less material to be produced, resulting thus a lower price.
Brazed plate heat exchangers have a lower acquisition cost and a lower replacement cost, making them the more economical solution.
And their higher heat transfer efficiency allows them to have a smaller size, which means you will need a smaller space to install it. Read here a detailed argumentation of brazed vs gasket plate heat exchangers.
It’s simple, it’s because they are more profitable for them – they have a higher acquisition cost and a high cost for replacing the gaskets.
With a good protection against rust, chalk and other impurities the brazed plate heat exchangers are the more economical and practical solution.
And if the exchanger clogs, then you can wash it without dismantling it. For this you need to use a proper cleaning solution and very importantly, after you washed it, you will have to circulate a neutralizing solution. When done correctly this procedure poses no risk of breaking the heat exchanger.
You can read here more about clogging and here about cleaning a heat exchanger.