saw those myself...i would need 2 'sets' though (over $40, plus s/h)...i was trying to find a fairly cheap way to replace the cardboard coins that come with Machi Koro (i just hate using cardboard coins!)...
Your best bet for cheap coins is always going to be finding foreign coinage. Maybe Mexican Pesos? Euros are good but there's not a lot of visual difference (besides size) between low denominations.
There's always Canadian coinage too. Similar enough to US but (lower value hurr hurr) still visually distinct.