It is generally true that plants designed for low opex have high capex and vice versa. We might therefore expect that a plant built around PTD would be higher in capital cost than one using conventional distillation. This however may not be the case. Shown below is the major equipment involved in conventional distillation. The capital cost of the separation equipment must include the cost of the steam plant and cooling plant that serve it.
Shown below is the major equipment of a PTD installation. The SAM and the MED regenerator will have a greater capital cost than a simple evaporator and condenser. On the other hand the MED uses less than half the steam of a conventional evaporator, so the boiler and cooling tower are roughly half the size and capital cost.
At the time of this writing, it is not clear whether the conventional package or the PTD package would carry a higher price tag. The capital cost of conventional equipment is well known but the cost of a PTD equivalent is not. Studies are presently underway at McMaster University which should help resolve that issue. In the meantime it is not unreasonable to say that the capital costs of the two alternatives are comparable, likely within 15% of each other.