Well, I have not heard back from the Craigslist add with the 2010 with solar roof, so unless that changes, I think we are leaning towards a new 2013 Plug In due to the rebates and a dealer /Costco quote I got that put the out the door price at ≈ $27,175 with tax, lic, $2750 Toyota rebate, 2500* Fed and $1500* Ca rebates (*though the money comes later: tax time and 60 days respectively). vs. ≈ $21,000 used ($20K - 39K miles) with tax & lic for a Prius Three. THough the 2014's (per Wikipedia) are due to arrive in Nov. at $2,000 less MSRP (per Wiki). I guess that is why Toyota is giving $2,750 of 2013' until Nov 4. Wiki says there are basically no changes to Plug In for 2014, so I guess $750 less for a 2013 vs 2014 new.
I would think you can get more than $750 off buying a '13 versus a '14. The dealerships are antsy to clear out the '13 models. Fight them hard on that.