I have an "AM" series, seems like it was a $1300.00 option in Sept, of 2008.

http://www.equalizersystems.com/Horse_Hydraulic.asp

Realize that on E-bay you are getting probably the rock bottom price on the Jack. You probably still have to pay frieght to get it shipped to you.

A dealer has already paid frieght, maybe some interest to have the product sit on the shelf and yes he expects to make some profit for selling you the product and having gone to the trouble to investigate the various brands and lean the Plus/minus of each brand.  Most add on options ( car dealer, trailer dealer) have much greater price margins than the original trailer itself.  That's why truck dealers  love to sell you the dealer add on options. ( bed liners, custom wheels, lift kits, custom radios etc) because they make more money ( Higher percentage) on the accessories than they do on the sale of the truck.

You probably can buy a hydralic jack online cheaper, but if you get the wrong product and have to return it, you could end up eating frieght 3 ways. It's up to you to decide what is a fair price for the service the dealer offers. If you are comfortable, source the product from the best price and do the job your self or hire somebody mechanically inclined to do the install for you.

I had a friend buy a new trailer last summer that cost well into 6 figures. He bought his own HiTies and had the fellow who does all his trailer maintenance install them. This fellow does not sell trailers, but comes out to your farm and does bearings, brakes, minor welding, He installs the hydraulic jacks, couplers etc. He has just made a business of instaling various accessories on trailers or servicing them.  He installed the HiTies my friend had bought online, did it improperly since it was his first time installing them, The first horse that gave any kind of rresistence, pulled the HiTie off the side of the trailer and left a gapping hole in the trailers aluminum.  Sometimes you just don't wan to do things twice in order to get them done right. I've never installed a jack on a trailer, I have no idea whats involved in the process. What caveats to watch out for.  But if I had to guess, I would think it's a pretty straight forward process of jacking the trailer up, unbolting and removing the old jack, replacing the new jack, bolting it back into place and connecting the power to it. But you would sure hate to do it wrong and have the jack fall off while you were reaching under the trailer to hook up your sewage drain line and have the trailer fall on you.

Another thing to keep in mind; the dealer may be figuring in the things that don't come with the jack. Battery, box, battery cables, hydraulic fluid, and necessary parts to mount the jack. And verify with the dealer what their $1400 includes. 

By the way...Equalizer and Big Foot are all I know that are out there, and personally I like the Equalizer better.

First off, where you are located will make difference on the price too.

I agree with the remark that Tresvolte made, 

By the way...Equalizer and Big Foot are all I know that are out there, and personally I like the Equalizer better.

I bought the Big Foot for our last trailer and paid 1650. installed with an extra power cable for more power.  Was LOUD when lifting and lowering the trailer.  Then sold it on ebay in Dec. 08 for $800 or $850... 

We have a Sundowner now with the Equalizer jack with a manual overide and like it better.  Is much quieter and smoother when lifting and lowering the trailer.

My opinion, you might find a bargin on ebay or direct, but actually in the long run it may end up being cheaper finding a dealer that has or can order the jack and install it so you will not have to do the foot work and hope you order the right part.