the lot purchaser will ultimately pay that fee.

True. Consider, however, that if a developer builds his own treatment facility the money is spent "up front" and not recovered until all units are settled.

Let's say a plant would cost $3 million while getting into OP will cost $2 million. Immediately the developer has reduced upfront capital costs by $1 million. Not only does he save the $1 million, but also any possible construction loan interest over a 3 to 5 year build out period.

One might also reasonably expect the cost of homes would not be reduced by spreading around the $1+ million savings to purchasers.