You should be able to find a used T'nA Toby for around 5000 yen ($41.00 USD)without a box, but most likely pay 5-6x that for a new one W/box.
I just picked one up off eBay used without a box that works perfectly for under $20!!
The Diesel 10 is actually more common to find with it's box than Toby, but is still around $350-$500 USD for an unopened one.
A used D-10 without it's box goes from $50- $200 depending on its condition AND FUNCTION.
Note: Of the 6 T'nA models Thomas,Percy,James,Toby,
D-10,Gordon,& Henry...
TOBY, D-10,& JAMES are notoriously delicate, and it's very hard to find a used one that FUNCTIONS properly or isn't broken. The interworkings of these trains are a bit complex and troubleshooting and repairing them can be difficult as well.
Hope this helps