Amazon.js

// ==UserScript==
// @name         Amazon.com auto-place PS5 Order
// @namespace    http://myles.empty.best
// @version      0.1
// @description  more bags
// @author       Myles "Empty" Best
// @match        https://www.amazon.com/dp/B08FC5L3RG
// @match        https://www.amazon.com/gp/buy/spc/handlers/display.html
// @require http://code.jquery.com/jquery-3.4.1.min.js
// @grant        none
// ==/UserScript==

// ONLY WORKS ON PAGE https://www.amazon.com/dp/B08FC5L3RG
// So load https://www.amazon.com/dp/B08FC5L3RG and wait

async function wait_for(query) {
    while(true) {
        var node = $(query);
        if(node.length != 0 && node.is(":visible")) {
            break;
        }
        console.log("" + query + " not available yet, waiting.");
        await new Promise(r => setTimeout(r, 500));
    }
}

async function press_button(query) {
    await wait_for(query);
    $(query).click();
    console.log("Button " + query + " pressed");
}

async function reload_later() {
    await new Promise(r => setTimeout(r, 10 * 1000));
    console.log("refresh");
    document.location.reload();
}

async function product_page() {
    await wait_for("#add-to-wishlist-button-submit");
    reload_later();
    await wait_for("#price-inside-buybox");
    var price = $("#price_inside_buybox").innerText.substring(1,$("#price_inside_buybox").innerText.length);
    console.log("Available for " + price);
    if(price <= 550) {
        await press_button("#add-to-cart-button");
        document.location = "https://www.amazon.com/gp/buy/spc/handlers/display.html?hasWorkingJavascript=1";
    }
}

if(location.pathname == "/dp/B08FC5L3RG") {
    product_page();
} else if(location.pathname == "/gp/buy/spc/handlers/display.html") {
    press_button("#placeYourOrder1");
}