The answers will surprise you.
On Ebay, these are closing for $12-14. That's a far cry from the $22 we were seeing earlier, which was a far cry from the $30 we saw when Modern was announced. Blood Crypt is $9! Yesterday, a set of Steam Vents closed at $12.50 apiece!
I'm giddy because I just snagged two Godless Shrines for $24 total on Ebay. I've been looking at prices on shocklands and this is the time to get into the real estate market.
The market is acting really irrationally and is correcting itself in ways I haven't seen before. Here are the facts: Modern is a format. There is nascent tournament support for Modern and a developing online community for it. Modern requires some numbers of shocklands for most decks. However, people are getting rid of their sets!
For some reason, there are a lot of auctions for shocklands going up. This is foolish to list and you shouldn't be selling yours right now if you can possibly hold them. The architecture of Ebay is such that you can set a low bid and a buy-it-now price and have the BIN go away as soon as people bid, or you can set a grossly high opening price, which means nobody will bid and the item will not sell. Thus, a lot of people are resorting to auctions to get their things out of the door. There are great opportunities to profit from this, and here is how.
Condition, Condition, Condition
I am assembling playable sets of shocklands at the moment. This doesn't mean that I need four of any of them and it also doesn't mean that I care too much about how they look. People have been listing played cards in the past few weeks, and those are great deals for people who just need the cards for tapping purposes. You must carefully read auctions; I've nearly bid on auctions, only to realize that the cards are beat, and had to adjust my maximum price accordingly. You can also get good deals if all you are trying to do is get candy for your trade binder.
Good Timing, Bad Timing
Another strange thing is that these sellers have not selected to have their items end at reasonable hours. What this means is that people can't stay up till 4AM to see the auction end and they won't bid on it. These are frequently underpriced sales, and you can get on top of them by getting last-minute bids in. If you don't want to stay up that late, USE TECHNOLOGY.
There are a wide variety of sniping programs available. I'd list some, but I am currently evaluating them myself! I can tell you to be careful and select secure ones and that there are enough free schedulers that you shouldn't be paying for them to place bids. These let you get in last-minute bids, while keeping a sane work and sleep schedule.
Research and Patience
These two skills go together very well when you're aiming to snag some new shocklands. If you're looking for prices, don't use the shortcut of BlackLotusProject (it's been broken for a long time) or store sale prices - neither are market-accurate. Use completed listings for your target. Set a reasonable range that you're willing to bid in, and stick with it! I have seen Verdant Catacombs sets, which I've also been trying to assemble, coming and going for $26-40 per set. That $40 person didn't do their research and they overbid, not realizing that there are about five auctions for sets closing daily. With a scheduler program, you can make sure you are bidding on all the action. That means you're less committed to winning one auction and you are more disciplined with your bankroll. More auctions for the same cards will come around. You will win what you win in your budget. I've seen Temple Gardens go for $9; someone won that card, and it might as well be you!
Exploring Other Venues
Stores are criminally overpricing their shocklands right now. Traders are too, because they are unwilling to admit that their inventory has dropped in value. One of the best places to look is on www.MagicTraders.com and specifically, on their "For Sale" forum. There, you can see people each week who are selling cards, for cash, through Paypal, with little risk for the intelligent buyer. Another advantage is that there is a little bit of price flexibility on it. You're welcome to ask a seller to come down a little on their prices, especially if you point out recent closing auctions. Be polite, be nice, and know that sellers are more willing to knock prices down if you are ordering a large quantity from them.
It is worth stocking up on a few filter lands, since there are some decks - Melira comes to mind - that prefer Filters over Shocklands. I will be paying a lot of attention to the new MTGO Modern Dailies, which will use the new banned list on 10/12. Those will be a big driving factor for format intelligence, and it's worth paying attention to filter lands that pop up in there that cannot be explained away with budget considerations.
You can expand this information to other elements of Ebay purchasing, though working with shocklands has been a good introduction to this for me. Best of luck!