The side angle isn't great but it looks very like my ideal VSD, D rings on cantle end the same too. (Mine is rebadged by local saddler and has velcro blocks)
tree should have a serial number on it you can check.
I paid £600 for an Ideal Event (that looks a lot like the one in the photos) 15 years ago. It's still in great condition and the saddler who fitted to Archie then, fitted it to Charlie earlier this year. He said he would probably still be able to sell it (fitted) for about £500 so somewhere around the £400 would be about right I'd think.
Yes it’s the same as mine which cost £250 + £20 postage from eBay 10 years ago and still as good as new would definitely get another ideal event-saddle