I've bought quite a few pipes and tobaccos -- and guitars -- on eBay. And I think if you really want the best chance of snagging something, you really should use a sniping service. (I've used BidNip in the past.) Don't be put off by the fact that many eBayers use such services; they're extremely handy.
I'll also say, though, that even if you just use eBay's built-in bidding service, be sure to put in the maximum you're willing to spend. I know that sounds like a "Duh!" tip, but if a pipe or a tin ends up selling for more than that, you can take comfort from the fact that it went for more than it was worth to you.
A couple of other thoughts: If a pipe/tin has a "Buy It Now" option, and the price is reasonable to you, buy it. As soon as a single bid is placed on an item, the "Buy It Now" option disappears. (And often folks will place a very early bid solely to get rid of that option.) Highly desirable items will often go down to the last few seconds before any real bidding begins, because no one wants to jack the price up along the way. But whether you use a sniping service or eBay's own auto-bid feature, your bids will be part of that frenzy, up to the maximum you've stated.
Finally, don't be afraid to ask sellers questions. If a photo is unclear or something isn't mentioned in the text that you're curious about, ask. Often, a seller will be happy to post or send you additional photos and information. And be sure to scroll down far enough to see if any questions have already been asked/answered, in case your particular concern has already been covered. (These can even be good for an occasional laugh. I recently sold some GLPease Syrian tins on eBay and had a guy from overseas ask if I had any more tins. . . and if I'd be willing to save them for him when he visits the U.S. in April, since my listing stated that I wouldn't ship outside the U.S. Alas, I had to say no.
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Bob