Because they can. Propitiatory connections and dimensions, certified safety ratings on all the used materials, operations and the assembly - not to forget a very heavy duty (try to imagine how many gallons of coffee each machine will brew just on one day).

7k to 20k are not a big deal for an airliner spare part. (and of course they get repaired...)

Have a look at the price of industrial coffee machines for large catering companies and then add the "needs to fit into an airplane and be allowed to be operated at 39k feet" into the mix.