A simple will done by a notary will cost you from $100 to $300 US, depending on the Notary. For this you will have to speak Spanish since according to Dominican law (article 972 of the Civil Code) a will before a Notary must be dictated by the testator and written down by the Notary.
If you do not speak Spanish, your only choices in the Dominican Republic are a holographic will, which must be entirely handwritten, dated and signed by the testator and can be written in any language; or a mystical, which in essence is a sealed holographic will delivered to a Notary for safekeeping.
A foreign will is valid in the Dominican Republic but some of its provisions may be reduced or voided if they come into conflict with Dominican rules of public order, such as forced heirship rules.
If you have children, I recommend preparing a will, even if, as in most cases, the inheritance will go to them in equal shares, as in an inheritance that is intestate (without a will), in order to prevent the spouses of the children from getting a share of the inheritance. Under Dominican law, “movable” property (cash, stocks, bonds, etc.) when inherited by a spouse is community property, unless the testator has expressed otherwise. Most lawyers/notaries are not aware of this...unfortunately, for their client's children.