For laptops, anywhere here is over-priced and under-spec. Buy from dell on line or other US supplier and ship via EPS to their Miami address. Angie at EPS should be able to give you a price on what to expect for tax's and shipping charges. Better yet, if you know someone coming in, ask them to pick up something in the US and bring it with them.
The best place I have found to buy electronics in Santiago is at Prodacom. The actually sell things for very reasonable prices and have the prices marked.
I think some of the people here finally are learning that selling for cheaper will increase volume and thus profit which is SO SO different from the Dominican mentality of trying to get rich by selling at high prices and low volume. I guess the "intuition" must be telling them it makes more sense to do it this way.