It seems you can chat with eBay through Google Assistant if you're curious to know the price about something and don't feel like opening the eBay app or website to complete the search. Though it's not clear how widespread this feature is in terms of how many people have access to it, it does seem to be enabled for some users, and you can view a few screenshots below of what the interaction looks like, which includes a different voice coming from the speaker than the one used when talking to Assistant, and the familiar blue eBay logo sitting inside a colored chat bubble in place of the four colored dots that are usually there.
While available now, the eBay chatbot seems to either be in an early stage or just a tad bit buggy. It isn't always consistent with the responses that it gives, and it doesn't seem to have answers for you relating to the price of the item you're asking about for every single item even when these are items that you would or can currently find on eBay. A question asking about the price of the Chromebook Pro resulted in a response saying that eBay couldn't help. Yet a follow up question asking eBay about the price of the Chromebook Plus garnered the standard response that you're supposed to get, which is the eBay chat bot asking if the item you're inquiring about is new or used.
It's also worth mentioning that the trigger word to get the chat bot to activate seems to be inconsistent as well. Once a conversation with Google Assistant has been started you should be able to simply say "ask eBay" and then the bot should respond by saying "I'm the world's price guide. You can ask me what anything is worth." However the ask eBay trigger never once seemed to bring up the appropriate eBay response, or any response for that matter. The chat bot only seems to be active in the Google app or by directly opening up to Google Assistant by speaking to it or by long pressing the home button, while support is not available for Google Assistant inside of the Allo chat app version. It looks like the only thing you can talk about with bot are the prices of items, so if you need a quick answer on what something may cost on eBay, who better to ask than eBay. It is worth noting that there seem to be a couple of requirements for the eBay chatbot to be available, and this includes the newest version of Google Play Services as well as Android 6.0 Marshmallow or above.