I have virtually identical car to you, dyno's at 198rwhp, also Zetec with full motorsport equipment on Pectel and TWM ITBs.
Given that it was ~$84K to build, I think your price is absolutely inline.
They are still the same price, or more. The 620R uses the same chassis, so nothing to be gained buying more recent.
Best of luck.
The only thing that may convince me to sell mine is 620R, although frankly, I don't see a need for more power than 200rwhp.