Amelia,
Here in the US of A people are obsessed with the "modern" throw away computerized plastic wonders. ( That is my attempt at sarcasm ) and treadles are honestly cheap.
I have 5 functional treadles right now and the most expensive one was a 1911 vintage Franklin in a parlor cabinet. I paid around $180.00 USD for it and that was really too much. But I wanted it and had the money at the time. My other treadles I've not paid over $100.00 for any of them even adding on repairs and parts.
Honestly I wouldn't spend the $250.00 for them. BUT .... I'm not in AU so that changes things a lot. If the newer Singer is in good shape that might be the going price. But I've read the quality of the new ones varies a lot. Some are good, some are junk.
Joe