Running an online store does not have to be expensive. You can use a free trial or even use commercial ecommerce software for free (as long as you don’t sell more than X items). And there os also open-source software which you can download for free and host on a server.
If you choose dropshipping, it does not cost thousands of euros to have your online store filled with all kinds of products. That is because you only pay for products that your customers order. And if your selling price is higher than your purchase price, you will have a good profit margin.
But, running a great online store is a different ball game. If you want to have success with your online store, you will have a hard time achieving this without making some serious investments. Investments in your software, your marketing, your products, et cetera.