Did I do the right thing?

Another E-bay situation came up yesterday. A single seller had about 15 lots of maximum cards up for sale, at a start price of $1.99. I was planning on bidding on them just before they closed. I noticed that earlier in the day, someone had bid on all the lots I was interested in. I can't be 100% certain that it was the same person bidding on the lots, but it is highly likely. I bid on the first one, and I bid it up to about $15, before giving up and moving to the next. The same thing happened on the second and third lots. At this point, I gave up on the rest of the lots. I could have bid them all up to the most I would pay for the lot, but I figured the other bidder had bid higher than I was willing to pay on all the lots. I didn't think it was worth it to just drive up the price he would pay, without any chance of me winning the lots. Now, looking back at it, I am wondering if I did a disservice to the seller? He got less for some lots than he would have if I had bid on them. Also, the buyer got a better deal then he would have, and now may have more money in his stamp budget to outbid me on or drive up the price on lots I want in the future. without knowing the buyer, I can't know if it is a zero sum operation for him, where he has a fixed amount to spend, or if he is buying to resell later, or what the situation really is. As an occasional seller, I would hate to have a potential bidder on some lots stop because of what other lots went for. After all, it is not like it cost me to bid on items that I don't win. I guess the lesson I take from this is to not list too many lots that are similar at the same time, or risk losing out on potential bidders. Especially on E-bay, where most lots have a low start price and rely on having bidding wars to establish the value of the items.