In my country developing a full website is very cheap, it would run for about 700-1000 USD to have it up and running with Open Cart, with no monthly fees. Is there a reason I should consider using Shopify and do it myself? Is Open Cart comparable to Magento? From what I can see the agency is not bad, this is one of their websites. http://www.koxisonline.com/ Thanks in advance for your reply.
Developing the website is the least of your concerns.
If you are operating an online store, building trust and confidence with your customer base is critical. So, when choosing a shopping cart to run your store, performance and availability are key.
When you use a quality, paid service like Magento or Shopify (or the myriad of others), you are paying for the solid infrastructure, the ongoing development and support.
With an open source cart, as you said you will have I do it yourself. You may not have the monthly subscription fee. But, you will have maintenance and development fees. You will also have infrastructure fees - if you plan to do it right.
If you would like to discuss this more, schedule a free call using my free consultation code below. I provide up to 30 minute calls at no charge for first time callers.