It’s a bit high for a troub that old that’s not in excellent shape, in this current market. As an example, a student of mine recently got an almost-new Pratt (more like a prelude) for 2K.
In your situation, I’d consider the fact that many harp shops will give you the full value of a new lever harp you buy from them on a trade up to a pedal harp if you buy it from them.
If your daughter does move to pedal harp within a year, $2400 comes to $200 per month, not including new strings etc. That’s more
than a rental would cost and most harp stores will give part of your rental towards a pedal harp purchase. Unless you want to keep that harp around after she’s playing pedal, it doesn’t sound like a hood investment for your purposes.
But if you buy a 2nd hand harp at a fair price you can surely sell it on again for what you paid leaving the monthly cost considerably under that of rental.