I always say I don't need a backhoe. I dug a trench the other day. Turns out there was a hard pan 3 inches under the surface. I needed 12 inches for drainage pipe. And 30 metres long (90 feet). Full day of digging, using crow bar on every inch of the ditch. Probably could have used a backhoe that day.
Probably not $9K of value, and I don't dig ditches very often, but I would have enjoyed it.
I also rented a Kubota mini-ex over the weekend, destroying a concrete water tank, and digging a hole for the replacement plastic tank to be half-buried. Definitely couldn't have done that with a backhoe. The hydraulic hammer for breaking up the concrete wouldn't have had enough flow on a backhoe, and I had very limited space - a zero swing excavator squished in, I had a lot of difficulty getting my tractor without backhoe into the space at all.
Horses for courses. If I did a lot of digging I think a backhoe would be a great attachment. For the money though, I'd probably get more use from a gang mower like this:
https://www.nzmowers.co.nz/hydra5-5-gang/