I for one would rent a different foil brand for a weekend to see how it performs.

In other sporting disciplines you can rent gear, snowboarding, surfing etc

it might be a better option than 4K outlay and then selling for 50% loss. Guess I'd want a couple of wings to try though.

Shops often have demo kit you can use , also demo days are held now and then.

yes that's a good idea, a test centre with guaranteed wind/waves with a good range of foils and wings to mix it up for a week.

Trying foils is like dating right, the first couple of times is fun, all shiny and new, but then reality kicks in

Also as mentioned previously having the conditions right when you do demo (if you're lucky enough to)

If not shops, I think it would be great if the local brand ambassador/representatives would rent or lend different foils. If I could try a few foils I'm pretty sure I'd spend more money knowing that I like the feel of a foil and have a sense of how much breeze it needs at my weight, etc. They could even adopt a subscription model where you either pay by the month or year to be able to demo as many foils as you want. Probably a pipedream......

I'd shipped my gear back to Australia and at one of the local crews had organised a day on the water. They were kind enough to let me use their gear while they had breaks. On the proviso "you break it, you own it"
We've winged together for the last year and wind was probable 10-14kn and I was able to try Schwinn 1400, Armstrong CF1600 and HA925, F-One Phantom 1480 and Eagle 1090. I also used a 6m, 7m and 8m wing during the afternoon. Conditions were pretty much the same all afternoon so comparison was easy.

As it's not always easy to demo gear, it may be easier to arrange something like this locally.

What did I find after trying all these foils?? The gear I have ( Naish ) performs as well as each brand and size I tried on the day.