When you're in doubt, try to contact their customer support. Services and websites that are dodgy and going down will have slow support response and the websites that are scams will never reply at all. But id suggest you to use the ones that are legit for sure, even if you pay a little bit more, you know you won't lose that money for sure.
What if they respond quickly? Does it will save their name from being a scammed company?
OP as far as all responses here concerned, I think you know now the answer. Also I will just add, any kinds of websites that have offering products or selling things or in other words, a merchants, the login was must be secured and verified (SSL) because it was confidential. Plus the fact that you will placed an order and money is involved, it must be all encrypted but the site doesn't have that kind of security to the sections where it does have e.g login page and purchase order page.