Most of the domain name market is open to competition, and hence you can shop around. You are not giving at least a ballpark of the current prices you are contemplating so it is difficult to know how far you are from example from registry prices.
However, in shopping around, no one else seems to offer what I would consider reasonable rates.
Maybe because this is such coming out of registry prices, that registrars have to forward to customers, plus their own margin...
Did your price really changed so much from the registration? Did you register it "normally" and not through some registrar or registry promotion in which the creation can be far less costly than renewal and hence you now get a bad "surprise".
A friend was explaining that .tech is a "premium domain"
This is incorrect, at least for a standard definition of "premium".
.tech is just one of the 1500+ new gTLDs that ICANN accepted, and indeed its prices are basically free to be set by the registry, whereas
.com/.net prices are more regulated. But you can find some new gTLD prices far below
He was saying that he always pays the same every year,
That is not even true for
.com, as there are yearly price changes (always up), but registrars may not reflect that to registrants, it is up to them. The registry, Verisign, changes its prices next September for example: https://onlinedomain.com/2021/02/12/domain-name-news/verisign-will-increase-the-com-price-from-7-85-to-8-39/
So prices change, everywhere.
Or, perhaps, .tech is different in some way from .com in terms of pricing?
As written above, new gTLD contracts give more leeway to registries in setting the prices, while other registries do not have so many liberties... but they are working on aligning themselves.
Compare this from the new gTLD contract (https://newgtlds.icann.org/sites/default/files/agreements/agreement-approved-31jul17-en.html):
(a) With respect to initial domain name registrations, Registry Operator shall provide each ICANN accredited registrar that has executed the Registry-Registrar Agreement for the TLD advance written notice of any price increase (including as a result of the elimination of any refunds, rebates, discounts, product tying or other programs which had the effect of reducing the price charged to registrars, unless such refunds, rebates, discounts, product tying or other programs are of a limited duration that is clearly and conspicuously disclosed to the registrar when offered) of no less than thirty (30) calendar days. Registry Operator shall offer registrars the option to obtain initial domain name registrations for periods of one (1) to ten (10) years at the discretion of the registrar, but no greater than ten (10) years.
(this is basically the only condition: announcing price changes)
.com has currently (https://www.icann.org/en/registry-agreements/com/com-registry-agreement-1-12-2012-en):
(d) Maximum Price. The Maximum Price for Registry Services subject to this Section 7.3 shall be as follows:
(i) from the Effective Date through 30 November 2018, US $7.85;
(ii) Registry Operator shall be entitled to increase the Maximum Price during the term of the Agreement due to the imposition of any new Consensus Policy or documented extraordinary expense resulting from an attack or threat of attack on the Security or Stability of the DNS, not to exceed the smaller of the preceding year's Maximum Price or the highest price charged during the preceding year, multiplied by 1.07.
(so the price is fixed in ICANN contract, and can only be changed by registry in specific condition and percentage)
I naively thought that, being somewhat new and obscure at the time, that a .tech domain would be cheaper. Was I wrong in this thinking?
Not wrong, just forgetting we live in a capitalistic base society. The aim of a registry is like any other company: please its shareholders and hence increase profit, and some are listed in various stock markets. As such they should just find the sweet spot in prices that let them sell as many as possible and be profitable.
Some technical geeks will tell you that a domain name is just a row in a database (which is really an oversimplification that is not useful in a debate), and as such should cost like $0.10 per unit, with price decreases as volume of domain increases because of scale benefits (ironically it is quite the opposite that happens: there are always more and more
.com domains and yet the unit price at registry always increase, and never decreases... except if you take into account that at the beginning of all this, with Network Solutions and even before registrars existed, it was $70 for 2 years so on that view you can consider today's prices to be quite a good bargain instead).
Asking in general. This is just how registration for domains goes?
Yes, at least in gTLDs and specially the latest round of them as ICANN mandated applicants to be for profit companies only. In ccTLDs it might be sometimes different because the registry can be non-profit in some cases, or in contract with the local government that can weight about pricing issues and for example mandate that the price is just "at cost" for the registry, so that some ccTLDs did saw price decreases in the past (but then studies and past experiences have shown that "near free" domain names is not a good idea either, search back for the .INFO promotions that got the TLD marked as unwelcome in many access lists, because by being free it was immediately abused by all sort of criminals).
Of course, it's well known that some domains are quite valuable.
This is a whole other can of worms: premium domains.
Many registries have them, in various tiers and prices, again everything under their control so with a lot of variations among them.
This particular domain is a rather obscure one for which I've never even set up any web hosting.
But is it considered a premium or not at registry? Your registrar should be able to tell you that. As well as explain why their prices increase, which is then an information you can take into account to move it elsewhere or not.