She is one of the most popular villagers, so she probably wouldn't go for cheap unless someone was feeling generous. Beyond that, once a villager moves out, you need to cycle through 16 other villagers before the same one can return to your town. I'm sorry that she left without any warning.
If I'm not mistaken, these types of threads aren't allowed. You'll have to use the 'Looking For' thread that's already been made, and you'll have to go through the cycling process first before getting Phoebe back, and 10k igb wouldn't be enough for any villager imo..the lowest I've seen even for tier 5 villagers is 100-200k igb