Most of the twins you can expect at least $15 for them MOC. Unless you have the second set, you won't get much more than that. Giggles and Wiggles are a more common set to find, so they aren't very high in price. You may get lucky, though!
I got my Berry Bright moc for $7, but that was when hardly anyone bought G2s. I think $10 is reasonable as well... and the twins usually run 15-20, although it depends on when you sell them, because there was a time where everyone wanted the g2 babies and the prices went up a bit.