нужно чтобы считывало value только из выбраного radio
<input type="radio" name="radio" id="checkbox" value="2830"><span style="color: #677788; font-family: arial; line-height: 20px; text-align: justify;">
Galileo</span>
<label for="radio"></label>
<input type="radio" name="radio" id="checkbox2" value="2810"><span style="color: #677788; font-family: arial; line-height: 20px; text-align: justify;">
ADM 600</span>
<input type="radio" name="radio" id="checkbox3" value="1800" onClick="toggle_visibility('Dop')"><span style="color: #677788; font-family: arial; line-height: 20px; text-align: justify;">
Teltonika 1100</span>
var checkbox = document.getElementById("checkbox");
var checkbox2 = document.getElementById("checkbox2");
var checkbox3 = document.getElementById("checkbox3");
var count = document.getElementById("count");
var result = document.getElementById("result");
var price = 0;
price += parseInt(checkbox.value);
price += parseInt(checkbox2.value);
price += parseInt(checkbox3.value);
price += parseInt(count.value) * parseInt(result.value);
result.value = price;