Hello, rawsushi!
Are you trying to make a lot of money selling things via eBay or Amazon, or just some money now and then? I do know a person who made his entire living for a number of months selling costume jewelry via eBay that he would find at garage and rummage sales. If a person sets things up for themselves so that all is kosher with tax authorities and the government(s) concerning exports and imports, making money selling things on the Internet can be good!
Your two links that you have in your post go to login pages for eBay. I just thought that I would let you know, in case you might want to change them. Not everyone has an eBay account.
If you would like to find out what would be best to sell on eBay or Amazon, you might try searches such as the following ones.
Hottest eBay Items - Google Search and
Hottest Amazon Items - Google Search
On this site, if you are wanting to conduct a poll that will get really good exposure, you're not really going to have a good cross-section of individuals who are going to happen to answer and/or respond to your question concerning what they might buy. Most of the persons on this site tend to stick to topic areas where they know that they will be able to answer questions really well or to those areas that are really popular. Then there are those that tend to stick mostly to the areas that are just about some type of discussion - really sort of like a chat room, then.
I don't want to discourage you from using eBay or Amazon, but would like to encourage you to take advantage of other ways, in addition to those two, that can be used to sell things via the Internet.
Using eBay or Amazon is okay, but there are many other ways that get much better exposure on the Internet as far as being exposed when people conduct searches for things that they might want to buy. What I'm saying is, that there is a much wider audience that a person could be appealing to outside of and beyond eBay or Amazon that is potentially better than using either of those two ways to sell things. Plus, these other ways don't have to cost a person anything to post on them what they are trying to sell.
A person can have any number of free websites or blogs in order to sell things. There are also many, many websites where a person can post things for free that they are trying to sell. Some of the websites are for ads that are meant to be worldwide in their scope for a target audience. How a person gets excellent exposure for when people do searches on search engines depends on how they have worded there ads and also how well a particular website gets exposure in general in searches. I have been doing online advertising for over three years now. Most of my business comes from the free ads that I have placed on the Internet.
By the way, in answer to your question, I would tend to buy things that are low-volume and expensive. My particular interests would be those things that concern art, music and antique/collectibles.