VRT is capped at €200 but as rez said, there are penalties that accrue for every day it's been in the country and unregistered, after the initial grace-period. The penalties are a percentage of the VRT cost and are designed to stop people driving on UK plates for months on end. There are ways of getting around that though. Like a receipt from a shipping firm that just happened to deliver last week...
from googling the phone number on the ad, he's hawked that beetle everywhere bar Ireland (VZI, carandclassic, thesamba, gumtree) for some strange reason. He's also offering to ship it to the UK for the asking price so either he's English and sees it as an excuse to make a visit to home or he's really eager to shift it. Google also tells me he's in Borris, Co. Carlow.