[Bob Bidonde]

Westach's prices are extremely high.
The most commonly used current sensing mechanism in DC ammeters is aa D’Arsonval meter movement. The D’Arsonval movement is a DC coil-type movement in which the needle is suspended by springs & centered between the poles of an electromagnet.
The price of D'Arsonval meters is dependent on the pivot point of the needle. The Model A's ammeter has friction type (metal to metal) pivot supports which reduces its accuracy. To the contrary, more accurate & higher cost ammeters will have jeweled pivot points like the Weston meters.
In my opinion, I see no value in spending big bucks for an ammeter or voltmeter for the Model A.
In the 2023 catalogs of the major Model A parts dealers, I notice that the stock 20Amp ammeter is not listed, but the 30Amp one is listed for less than $20.