Sometimes I have been able to find some good deals on used LEGO sets, however most of the time I spend looking for sets is trial and error.
I usually search from Toys & Games > Construction Toys & Kits > Lego to weed out most of the clone brands and sort by Best Match.
Are there any particular good search terms, web services or techniques that can make it easier to find LEGO bargains on eBay?
I don't think there is a single strategy that will always work - it all depends on what other people are looking for at the same time as you are looking. For example, I have seen Lego Maersk train sets (I'm a Train fan :) ) sell for $250 in certain auctions, but have managed to pick up one with extra power functions for less than that in a separate auction.
Here are a few things that might make your life easier:
Create searches and save them (you can even get notification emails for new finds this way). These are called "Followed Searches".
Use the tips and techniques in the Advanced Search section of eBay Help to refine your searches. For example, if you want LEGO but not Duplo, you could search for "Lego -Duplo".
Always compare with current retail values (check Amazon.com, shop.lego.com or brickset.com) if the set is still current
For sets that are no longer current - look at brickset.com to see what they used to go for. If you have the time, check out Bricklink.com and see how much the same set costs there, or, if you really have the time, use the Inventory feature and see if you can get a better deal just buying the set pieces :). For the popular holiday train (10173) for example, which easily sells for >$500 on eBay, the cost in pieces is typically around $200 on Bricklink, lower if you already have some of the critical pieces.
When it gets to bidding, look into using Sniping software, which allows you to place a bid in the closing seconds of an auction. This often helps you win auctions if no others are using snipes. JBidWatcher is a good starting point.
For bidding, check out what others have already bid ("Bid History") and also look at "Show Automatic Bids". This allows you to see who is really eager to get it and how often they have bid.
There are for sure other techniques out there, but these are the ones I find work best for me.
I've put together a basic web service that does this if you are specifically searching for bulk LEGO (e.g. 5 pounds of assorted bricks). It is available here:
https://joncraton.org/lego-by-pound/
It searches US eBay for bulk LEGO via a number of search terms. It then limits the results to only those for a which a weight can be determined from the listing title. It excludes all results for which the price + shipping is over $10 per pound. The results are returned sorted by soonest end time.
This has been very helpful for me in identifying bulk lots that are a good value, so I wanted to add it here as another method of bargain hunting on eBay.
I don't know about ebay, but I have used bricklink to get parts. I looked for an old Unitron set (Star Hawk II), and it produced an itemized list with links to each part, or group of parts. I was able to order small groups of parts from different vendors (other users) on that site. You may want to factor in shipping or use the terminology you get from bricklink to search ebay, as most enthusiasts tend to keep the vocabulary the same. Hope that helps!
The following is for complete sets:
First of all, I get a feeling for what currently is a "bargin". Prices for sets vary a lot throughout the year. Therefore, I do the following:
Search term: lego "set number"
Search options: auction, soonest end time
After a few auctions have ended, I already know what would be a good price for a given set. Then I save the search and look for promising auctions, with patience. Usually I don't follow "MISB, NEW etc." because I want to build, not put away sealed. I also watch out for "no minifigs" because that reduces the price significantly. I also don't care about the original box. Building instructions, on the other hand, are important to me.
Sometimes, missing parts come in handy when you know how to replace them (or already have them). Even simple missing parts tend to reduce the final bid.
Note: After a couple of months your bargin price may not be a bargin any more: Once, I didn't buy a used 42009 for around 110 Euros, now it costs at least 160. Too much patience is not good if you really want to own a particular set. :)
Note 2: I have never understood the "Best results" default. "Best" means that many other bidders are already aware of that particular item. Not good for bargins.
