CastError when using variables but writing manually the same query works

Question

I'm converting my price query into an array and then dividing them into variables to do a query with more than one filter per variable. The problem that i have is that doing this divition between the array and using them to do a query i get a CastError, but when i tipe the same string manually it works.

My model looks like this:

const mongoose = require("mongoose");

const productSchema = new mongoose.Schema({
  name: {
    type: String,
    required: [true, "product name must be provided"],
  },
  price: {
    type: Number,
    required: [true, "product price must be provided"],
  },
  featured: {
    type: Boolean,
    default: false,
  },
  rating: {
    type: Number,
    default: 4.3,
  },
  createdAt: {
    type: Date,
    default: Date.now(),
  },
  company: {
    type: String,
    enum: {
      values: [
        "Nike",
        "Adidas",
        "Puma",
        "Balenciaga",
        "New Balance",
        "Air Jordan",
        "Reebok",
      ],
      message: "{VALUE} is not avaiable",
    },
  },
  img: {
    type: String,
    required: [true, "Image must be provided"],
  },
});

module.exports = mongoose.model("Product", productSchema);

const { featured, company, name, sort, props, numericFilters, all } =
    req.query;
  var queryObject = {};

if (numericFilters) {
    const operatorMap = {
      ">": "$gt",
      ">=": "$gte",
      "=": "$eq",
      "<": "$lt",
      "<=": "$lte",
    };
    const regEx = /\b(<|>|>=|=|<|<=)\b/g;
    let filters = numericFilters.replace(
      regEx,
      (match) => `-${operatorMap[match]}-`
    );
    const options = ["price", "rating"];
    var arrayObjects = [];
    var secondObject = {};
    filters = filters.split(",").forEach((item) => {
      const [field, operator, value] = item.split("-");
      if (options.includes(field)) {
        if (field == "price") {
          if (arrayObjects != 0) {
            secondObject = { [operator]: Number(value) };
            arrayObjects.push(secondObject);
          } else {
            secondObject = { [operator]: Number(value) };
            arrayObjects.push(secondObject);
          }
          queryObject[field] = arrayObjects;
        } else {
          queryObject[field] = { [operator]: Number(value) };
        }
      }
    });
    queryObject.price.reduce((a, v) => ({ ...a, [v]: v }), {});
  }

  var firstPrice = queryObject.price[0];
  var secondPrice = queryObject.price[1];
  let result = Product.find({ price: { firstPrice, secondPrice } });

First price and second look like this: { '$gt': 150 } { '$lt': 300 }

Using this i the error message i get is: (node:11348) UnhandledPromiseRejectionWarning: CastError: Cast to Number failed for value "{ firstPrice: { '$gt': 150 }, secondPrice: { '$lt': 300 } }" (type Object) at path "price" for model "Product" I don't get why it shows the name of the variable and the object at the error message.

But if i type the query manually like this it works: let result = Product.find({ price: { $gt : 150, $lt: 300 } });