Small version with 2 different filters ~40€, big version with 4 different filters ~80€. All come without any kind of carry case / pouch. A bit expensive and lacking for that price tbh

I ordered a custom set a good time ago (months before the existence of this community) and the experience was comparable to yours.
I choose white mbk pbt and the laser engraving was really sharp and looks very good! Shipping was quite fast for me (8 days or something to Germany) but back then VAT was no accounted for during ordering (which I was informed of, no suprises there). So I had to pay VAT after receiving the package. Don't know how it's currently being handled though. Simon was also really responsive, so all in all a quite good customer experience.

The 2 pair of IEMs I use by far the most are my Blessing 2: Dusk and the Galaxy Buds 2 Pro (for convenience).

The Cheapino gets quite some love recently :D Saw a couple posts in the last weeks, really cool! I too built a Cheapino for myself and a friend who wanted to try out these ominous "ergo mech keyboards" 😁

Nice case! Basic but functional, pretty good for a first

Wow, really cool :D I'm wondering why you went with a straight line for the thumb keys instead of going for a curve (which so see with a lot of ergo keyboards). Is there any general benefit or is it just more comfortable for your hands?

That's a really interesting case design too! Cool to see that you're taking into account that one might bring it into the office or so and needs a "travel" case as well.

That's a really cool and funny solution :D

Honestly, not a lot of people in rented apartments can hear music that loud to "feel" the bass. If I did my neighbors would literally kill me.

Cool! I'm happy it actually helped you :)

I also own the Cheapino and made myself a keymap which is fully working. You can have a look at it here. Hooe that helps at least some bit.

Regarding the qmk toolbox: You can take the json file from one of the keymaps in tompis qmk_firmware repository and upload it in qmk toolbox. Then you can have the correct layout and you can configure it to your liking.

It's pretty straight forward though you need some soldering skills, especially for the little usb c connector. I used this site: Cable Guide in combination with YouTube videos of Cruzctrl.
In short: You need wire, paracord (for sleeving), optionally techflex (for the shine), some heat shrink, usb connectors and any connectors you'd like to put in between (in my case gx16 aviator). Then you sleeve the cable, put techflex on, solder the connectors, apply heat shrink and you're done. Though that's just a really short write up. It's not overly complicated but also not as easy as it sounds.

Thanks☺️

Thank you 😀

Cool design!

One of the best cheap (non-custom) options is the Alpine MusicSafe Pro (~25€).
If you wanna go for a custom hearing protection you're quickly into 3 figures. Here in Germany there are some vendors for custom stuff where you could get some "no name" custom or some brand stuff like the Alpine PartyPlug Custom for ~200€.
But with all custom stuff the price heavily depends on what exactly you want, from which brand and where you are ordering it.

In general I would recommend getting the cheap non-custom option, see if it works for you and if not you can still cash out for some custom ones. 25€ is not that big of an investment compared to the price of a custom set.

One of the cheapest options might be building a cheapino. It should be around 50-70$ all in all. Though it's completely DIY and not the best option for beginners.
You'd have to order the PCBs and all the other stuff yourself and build it.
If you don't want to or cannot do that, there are already a lot of good options in the other comments.

EDIT: spelling

Ohhh I didn't even recognize there was a little switch. Really cool! Thank you

That's a really cool build, well done! I'm wondering how you're using the trackball and mouse clicks. Do you use the trackball with your index and middle finger and have left and right mouse click on the thumb keys to press them with the thumb?

Regarding documentation, you could have a look at splitKBs Aurora series build guide. They made their own Sweep variant but it might just be similar enough to still use it as a nice build guide for your ferris sweep.
EDIT: It also has a part about installing batteries, power switches and all the other stuff needed for a wireless build.