I'd say "insane"!

Perhaps the fact that this is a "trainer" model made the price go up sky high.
As far as I know, trainer model instruments are a lot simpler to interface, probably working at 28V DC.
You still need to figure out how to connect it though ...
For other people still searching for an original "LOX" indicator:
I have built a 115V AC 400 Hz power supply and have the original LOX indicator working.
It is a bit tricky, but al you need (besides the 115V/400Hz power supply), is a variable capacitor with a range variation of some 40 to 50 pF. Then you drive that variable capacitor with a stepper motor.
The stepper motor is easy to control with any interface --> working original LOX !
One remark: wiring from variable capacitor to LOX is tricky and needs attention. Very sensitive stuff.
greetz,
- henkie