indirect water heater cost

I'm getting a condensing boiler for my house (Monitor MZ25C), and am considering replacing my gas water heater with an indirect heater feeding off the boiler. I was quoted $1900 for a 40-gallon tank (Buderus ST-150) plus installation, and live in Minnesota.
Does this sound right? It's much costlier then I expected. And assuming this is the going rate for these things, is it a reasonable purchase? There's supposed to last a very long time and be very efficient.
A final point is that here in Minnesota, single-walled boilers are not allowed by code, (except for some reason Buderus was just now allowed), which limits choices. And supposedly, double-walled boilers have trouble keeping up with the Monitor's output, which makes it cycle several times while heating up the tank.
Thanks for any feedback.
-- Paul
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