Pingu,
The first question I have for you is are the prices you're quoting American dollars or Dominican pesos?
The second question is are these prices per floor space? If for squared floor space does this include the area taken up by wall space or not?
Regardless, let's just assume for a moment that you would be happy with a house 10 meters by 14 meters. The price you quoted in plan A would be $60 - $65 per square foot or $ 90,416 - $ 97,951 for the 1506.947399 square feet/ 140 square meters.
Under the price you quoted in plan B, $300 -$700 per square meter would be $ 42,000 - $ 98,000 for the 140 square meters.
I was discussing construction prices on the below link with other board members so you might want to check it out;
builders
If the prices you are quoting are DR$ then the prices are excellent even with the poor construction that usually takes place in this country. If the prices quoted are US$ then you are being taken for a ride.
With the prices Hillbilly quoted you would be paying RD$ 2,100,000 to RD$ 2,800,000 for the finished product.(US$ 65,265 - US$ 87,500).
Read the link I posted above it might be enlightening.
Rick