I agree that prices tend to vary depending on the time of the year. This holds true not only on collectibles, but on everything from cars to commodities. But, I also think that now-a-days people spread their bidding out more. Competition has always = lower prices.
While I realize that ebay is not about to go bankrupt due to competition from JackpotAuctions...but, I do believe that there has been a significant impact in their stike business. A lot of strikes move through Jackpot, and as with any product, that has to affect the prices. The big winner is the buyer, they are getting what they want...and saving a few bucks at the same time.
Case in point:
Look at the active,(and closed) auctions on both sites on the new Palms strikes. For every strike that was sold on Jackpot, that's one less that sells on ebay,(and changes the current selling price). Many collectors already won the Palms strike at Jackpot days before the first strike closed on ebay. And if you look at the $200 Palms, many more sold on Jackpot than anywhere else. With a guy named NORM setting the price, (and quite a fair price at that).
I also notice that many dealers come to Jackpot and buy on a regular basis. They know that they will get the new strikes at Jackpot first, many of which then re-sell that same strike...some even sell it back on Jackpot at a higher price.
Another case in point:
We live here in the small town of Pahrump, NV and just last week, a new gas station opened. To get new customers,they offered their gas at about 10% less than the others,(all of which had the SAME high price). Now in a town of this size, there is only so much gas that will be bought. So what happens, the other guys lower their price...next thing you know, there is a "gas war" going on. Today, the price went down to 99 cents a gallon. The winner: the buyer
This is how business works, available quantity affects price. I have received several dozen emails from sellers on ebay stating that Jackpot is killing them, saying that they just can't get the prices that they used to. The strikes on Jackpot, for the most part, start at very fair prices...and who wants to spend $20 for a strike on ebay, that they can get for less on Jackpot.
It's quite simple, the cost of doing business on Jackpot is less than it is on ebay...those savings are passed on to the bidder.
I know it may sound like I'm pitching Jackpot, and I am...the strikes you want are there...the prices are fair...the sellers are honest. And if you keep your eyes open....sometimes, like with the McCarran and Stardust strikes...you will find incredible deals.
Of course, we can always use more sellers...and more strikes. That's an open invitation to ebay sellers that want to give Jackpot a try. And also to all of you strike collectors!

Just my opinion,
Dan at Jackpot!