One problem with most website related services are that they are either low quality services and some can even harm your website more than they will help it. Thing like buying backlinks on there are something that I would avoid because most sellers will basically put up a link for any website that someone pays them for.
This can mean that there are a lot of junk, spam, phishing, malicious or otherwise harmful websites that could have backlinks on the same site as a quality website.
As for submitting your website to search engines, those can be done for free by yourself so it would just be a matter of if you wanted to do it yourself or pay someone to do it.
I am not saying that all services on eBay are not good because I haven't looked through that section on eBay enough to see what's there, I am just saying that there are a lot of services that I personally would avoid doing for any of my websites.
This is something that you would want to really check into what you are getting exactly and if it's a good service or not and that can sometimes be hard to tell especially if you do not know enough about the service.
Sorry I can't give a more definite answer but if you find a service in particular that you are interested in then you can message me the link and I will be happy to take a look at it for you.