To really take a look at what is a reasonable offer you need to know what's out there, a simple Google search or two yields all the listings offered by the major
DVC brokers - 95 Saratoga Springs contracts on the market right now w/ asking prices ranging from $70 per point to $115.63 per point.
Of those 95 contracts there are 29 in size between 200-230 points.
There are 5 for 225 points, including the one OP is looking at.
So how do those 5 rank against each other? I find it helpful to monetize the status of the contract to get a real sense of the value of the contract - is it stripped or loaded? So to compare the 5 contracts I've assigned the going price that David's will pay to rent points - $11, as the fair market value of the 'extra' (banked) points or the 'missing' (stripped) points to compare loaded v. stripped contracts:
$80 March w/ 190 banked 2013 points x $11 = $2090/225 = $9.28 per point more valuable. $80 - $9.28 = $70.72 true value/cost
$78 August w/ 45 banked 2013 points x $11 = $495/225 = $2.20 per point more valuable. $78 - $2.20 = $75.80 true value/cost
$78 March no banked points but all 2014 points going forward - neutral thus $78 true value/cost
$78 February no 2014 points and only 99 - 2015 points. Seller has used 351 points (all of 2014 and 126 of 2015) x $11 = $3861/225 = -$17.16 per point + $78 = $95.16 true value/cost
$85 September no points until 2015 - but has all 225 points from 2015 thus add to the true cost of the contract by the points the seller has stripped from the contract @ $11 per point = $96 true value/cost
Just another way to try and compare apples to apples.