Right now you need about 3 months to get EUR 65 from 1 unit with 0.1 EUR/kWH (and it's too cheap for EU).
Any way you can check eBay auctions for the current S3 prices.
First, check your math. S3 produces ~$2.2-2.5/day minus ~$1 in electricity, but with +$0.3/day in heating savings, so net ~$1.5-1.8/day currently.
Second, the price on ebay is $200-350 with average ~$249.