Environmental allergies are curable? (Sublingual immunotherapy)

Also, this page on the Johns Hopkins Medicine website says:

The cost of a one-year supply of allergy drops ranges from one thousand to several thousand dollars, depending on the number of things to which you are allergic.

The medical consensus is that sublingual immunotherapy is inferior to the injected immunotherapy that has been used for a century. Did you try that as a kid? If there's reason to believe sublingual is better, that's good to know, but it sounds like you just don't know about injections.

Sublingual immunotherapy has an obvious advantage because people don't like shots. And it doesn't require a prescription. Indeed, one should be suspicious of a conflict of interest in the medical consensus. But injected doses are more precisely controlled, so there is good reason to believe they work better. And the doses are smaller, so the material cost is smaller.

Compliance to the schedule may be the main obstacle. It is not obvious whether doctor appointments make this better or worse. This probably varies between people.

I was allergic to acarids when I was a child, and this caused me a severe asthma crisis when I was around 10. I live in France, and I got prescribed SLIT by the first allergy specialist my mother found, so I guess it's quite a common treatment there. I took it for more than 5 years, and now 8 years later I don't ever have any symptoms of allergy.

My understanding (based on watching some YouTube lectures and talking to my allergists) is that SCIT (aka allergy shots) and SLIT are equally effective but (at least in the US) SLIT is not covered by insurance so SCIT ends up being a lot cheaper for most people. The main problem with SCIT is that it requires going to the allergy clinic every week for a while, then every month for a while over a period of about 3 years (but it is possible to speed things up quite a bit by doing cluster shots or double shots). I tried doing SCIT last year but my chronic illness made it too difficult to go to the clinic each week so I eventually had to stop (I imagine this won't be a problem for most other people). My allergy clinic gave me an estimate that SLIT would cost roughly $7000 total over 3 years, whereas SCIT for me was free with my insurance.

How were you getting SLIT for $25/week, how much did SLIT cost in total for you, and were the doses tailored to your particular allergies based on tests?

How long has it been since the treatment, in your case? A quick perusal of the top search hits for this treatment suggests that it (often? usually? sometimes? not clear) wears off after several years.