I cannot say a value for the cart and wings in the US. Although compared, pricing here is close to $500 in very good shape. Cheaper beaten ones for a good few less.
But, I would advise as kevinculle here, to have a look for yourself whether to keep the kit.
The cart may be the best cart for a heavy miter saw, the wings and saw can be used without the cart on a bench of your choice with the legs folded up. The wings can be used singular or in pair, also with other Festool accessories.
I’ve experience with DeWalt and Bosch miter stands (Which do set up in a sloping or uneven terrain) and they are unwieldy and heavy compared to UG cart and wings. The downside is (not) setting it up in uneven terrain.
The UG set might be better value in use than the potential money it will bring.