Note there's an "Everything Else" forum where lights are specifically a topic. Maybe a better place to ask?
I'm not an expert, but here's my experience. The lights in our pool were 14 years old when we moved in and working. They're all Pentaire:
- 2 Amerlites in the main pool: about $300 each
- 1 AquaLight in the spa: about $250
These use halogen bulbs and require hundreds of watts of 120 volt power. If you want to light the pool every night, not perfect. But for a party now and then, they're great.
As luck would have it, the AquaLight blew a bulb about 4 months after we arrived. I found drops of water in the housing. The seal must have leaked. Also, the @#_($@ installer had left no extra cable in the niche, which is supposed to be standard practice. I could only get at the bulb by disconnecting at the breaker box and pulling the free end into the conduit (with rope attached to pull it back). What a hassle...
Rather than trying for a fix by seal and bulb replacement with the short wiring, I decided to replace it. That was pretty straightforward. It went well, though a bit tense as there are ways to screw up that you don't want to try out.
Note that your old lights will need to be removed and the niches measured to determine what will fit. I've read that most niches accept most lights of the same diameter, but there are exceptions where a deep (thick) light won't fit a shallow niche.
You're right: the prices for some of the LED systems are outrageous. Light housing designs have been tried and tested with the high temp halogen bulbs for decades. There's no way swapping in an LED light source justifies the kind of prices being asked.
I note that since I was looking there seem to be some lower-cost options: 2x the halogen prices rather than 5x. My guess is they're Chinese copies, so reliability might be an issue.
Wish I could be more helpful.