Sean O'Brien has forsaken somewhere in the region of €220,000 per season to stay in Leinster "to win trophies."
O'Brien stood to earn about €600,000 Gross and €470,000 after tax in France, while his new improved offer from Leinster means he will earn €420,000 (before tax is deducted).
Of course, if you want to get cynical, you could allude to the Charlie McCreevy era tax break which means rugby players who remain as players in Ireland for a decade get to claim 40% back on their tax at the end of their careers. However, O'Brien is a few years away from that and his new contract is only two years. Plus, either way, there's more money in France.
Interestingly, because of European Commission quibbles, the regulation that Irish players have to finish their careers in Ireland to avail of this tax break was altered by the government last October. Therefore, Paul O'Connell, if he was so minded, could go and play in France and still claim back the 40% as he has played over a decade in Ireland (the rule change would have come as particularly good news to Peter Stringer).
So, that's the basic facts about the finance with absolutely NO FARM JOKES thrown in. Spare a thought for tabloids as they wont get to use that gut-bustingly funny and inventive 'Toulon Tank' headline for at least a couple of years.