it varies- they can go for like 10million IGB there should be a thread somewhere on here that shows the difference in IGB and TBT- since they can go for like pver 100TBT
It also depends if they are original (aka, starter clothes, house furniture, catchphrase). Some people love original villagers and I can understand them for having the 'fresh' feeling, or for having a nice looking villager instead of a house full of fossils and fish, wearing a Four-ball shirt and saying 'I hate my life' as catchphrase.
They can range from 70-150 TBT depending on that, and how many people are interested. That's why most of them are auctioned instead of sold.