What ETF and Hello Again said! I’m going to expand on that just a bit. Bear in mind that, with horses, YMMV. It varies a LOT.
In my experience, horse costs are a function of the following…
Age: The horses most in demand seem to be those between 5 and 15. You’ll probably pay more for one in that age range.
Talent: Whatever the horse’s job (cutting, hunter/jumper, dressage, reining, etc.), a horse that’s good at that job will cost more than one that isn’t.
“Ease of ride”: A well-trained (“made”) horse will cost more than something that still needs a lot of work (“green”). Likewise, a calm, forgiving, tolerant animal will usually cost more than a fire-breathing dragon that doesn’t tolerate fools (or beginners) lightly.
Soundness/health: Some horses come cheaper because they have maintenance issues (e.g. need corrective shoeing, joint injections, etc.), have a health condition (e.g. Cushings), or are limited in what they can do (e.g. they shouldn’t be jumped, galloped hard, or carry more than a certain weight). You’ll pay more for a horse without those issues.
You won’t be able to find a horse that’s great in all four areas without paying a hefty price tag. However, if you’re willing to take on an older horse that may have some maintenance issues or would never take you into the show ring, you can save some.
For a trained, pleasure horse over 5 years old, you’d probably pay $2,000 to $15,000 around here. Towards the lower end, you’ll find horses with more maintenance issues, who tend to be older (16+), and probably won’t take you into the show ring. Towards the higher end, you’ll find horses with fewer maintenance issues, aren’t so old, and may competitive in smaller or local shows.
If you want a horse that’s competitive at the bigger shows, you’re going to pay a lot more for a well-trained animal. But, since you indicated a good pleasure horse, you likely aren’t interested in more than the occasional, smaller show, if that.
As Hello Again said, don’t buy a horse until you’ve had at least a year of lessons. It’s good advice.
Placid, well-trained horses can have their moments of idiocy. You need to develop some riding practice and skill to handle those. You also need to learn the basics of horse care/maintenance. Even if you do full board, you are the primary person looking out for that animal’s well being. You can delegate a lot, but you need to know enough to do it responsibly (e.g. know when your horse is getting substandard care). There are thousands of good books out there, but nothing replaces hands on experience. For example, you can find hundreds of diagrams showing how horses with founder or laminitis stand, but many horses aren’t quite as obvious about it as a diagram.
Also, you may not really know what you enjoy before you try it. Maybe you think you’d be happy just trail riding only to get into it and find you’d like a horse that could take you over small jumps. Or maybe you want to go Western rather than English or vice versa. More importantly, you have to find out what type of horse best suits you. Some people prefer smaller horses. Others feel better on larger ones. Likewise, some prefer a horse that needs more prodding to get going while others like a horse that carries them a bit.
Finally, you may decide you really don’t like it that much after all. There’s nothing wrong with that. Horses, even if you board, are a big commitment. If you find you don’t have the time/desire to enjoy your horse much, you’ll still spend a lot of time and money caring for it. It may seem romantic and fun, but it’s not for everyone. Some people try it and get scared (especially if they don’t take lessons first). Others think “meh, not as fun as I thought.” Better to know you’ll enjoy it before taking the plunge!