Steam Market Total Counter at https://steamcommunity.com/market/

smtc.js

var sum = 0.0;
document.querySelectorAll('.market_home_listing_table:first-child .market_recent_listing_row .market_listing_my_price .market_table_value .market_listing_price span span:last-child').forEach(function (item, i, arr) {
    sum += parseFloat(item.innerText.slice(1).replace(/,/, '.'));
});
alert(sum);