I had a long response that included this that got eaten by the internet. That or the owner really does not want to part with the horse, but for enough money they’d entertain the idea.
As others have said, if the horse did not sell in Wellington in the winter, he’s overpriced. Or, as happened to me, the trainer I sent my horse to in Wellington was happy to have him on her payroll and she did a terrible job selling him. It was back in the days of FB allowing sales sites. I’d answer the ISO ads that he was a great fit for with a link for his sales site, and almost invariably what I’d hear was “I contacted her about Dobbin and never heard back”. She always came up with an excuse for why this happened. I was a bit overwhelmed, 1500 miles away with no idea where to go from where I was already getting taken advantage of, and that is very unusual for me. The expression that many who know me use to describe me is “doesn’t suffer fools lightly and has a highly tuned BS meter”. Or my favorite “You think she’s blunt now? Wait until she doesn’t like you”. He ended up getting injured and now lives on my dime, retired. But that is a whole other story not relevant to this situation.
Also as others have said, there is a huge chasm between PSG and GP, especially if you would like to compete. Spanish horses are renowned for their ability to do the “tricks” but not necessarily in honest contact, through, or even correctly. They are by and large smart, and once they learn something “wrong” it can be incredibly difficult to un-teach it. Friend of mine with a PRE spent YEARS getting a clean change on her horse. Horse learned it late behind and it was incredibly difficult to fix.
OP - you do not need to post it for public consumption - but try to honestly and brutally determine whether this horse has some holes in his training or if the issues are more with your inexperience with dressage that are causing the score issues. This will have a large impact on his ability to get to GP. Also be honest with yourself about how much time you want to ride versus having your trainer ride to keep him at least where he’s currently at.
If you need to take loans out to cover his purchase price and continued board and training, you can’t really afford him. Horses spend 22 hours a day looking for new and inventive ways to maim themselves. Be very honest with yourself if the unthinkable happens and this horse injures himself so that he is only pasture sound, what does that mean for your life and finances? I know it is a tough way to look at it, but what does it mean for the rest of your life if you go through with this huge purchase?
Remember, this is coming from someone who realistically should have gotten $40k for her horse after commissions, but instead, I am paying $10k a year for him to be retired, unrideable, in Florida. Could I find a way to afford another horse? Yes, but I am already stretching my non-horsey SO’s patience with the money going out to support this horse.
Hopefully not!
. I don’t know anybody still doing this anymore 
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at the time it seemed like a lot but now Im thankful everyday. We would have never been able to afford a 4th level horse. We got lucky- and I guess all those crazy horse camps helped more than we realized.
