The answer depends on the registry, hence the TLD.
So, in short, speaking about the generic case and not a specific TLD (see at bottom for specific data on .space:
registries are mostly free to price their domain name the way they wish; they typically define list of "premium" domain names, with specific prices; You also have EAP, which means at the start of a TLD opening (like right now for .dev), all domain names are available... albeit at a higher price than the normal price (the reason being marketed for that is that in this way this deters pure speculators and enable real users of the name to acquire it; anyone is free to agree or not with this explanation). You can of course also have premium names during EAP which means two extra fees to pay. But normally "premium" moniker just refers to name permanently on a special list that makes them be priced differently
the list of premium domain names and their prices is given (again: normally) to registrars beforehand and can typically be checked in real time through the EPP channel that registrars have to registries; domain names can be added to or removed from those lists, and prices can change too during time
typically registries define groups of premium names, and price all domain names at the same level for all domains in the same group; but you could as well have cases where each and every domain name is priced differently, again the registries have full control over that, and can even change things during time as they wish (for gTLDs, the ICANN regulations just mandate that they notify their registrars in advance if they change anything regarding pricing)
it is rare that the full list of premium domains names are public; typically they will only be known by registrars; so to know the real prices you will need to conduct some searches on registrar websites (I strongly suggest not to use resellers or third party providers there as premium handling is typically more work hence it may not be included into every provider registration path).
for some registries the price paid at creation is a one time extra fee, renewals will be at standard price (this is the typical case for domain names bought during EAP); but, warning, for some registries the premium price you pay at registration is the price you will pay for any subsequent renewal until you delete the domain name (at which point it can go back to the premium pool or become a generic one, no hard rule there).
All the above does not come out of registrars: it is registries' decisions to price some of their domains differently. Registrars have obviously to pass on this extra price to their customers... adding their own margins to it. And here you will obviously find various price strategies by registrars so like for everything else, you should look around before deciding where you shop.
Now for your other questions.
How do I find the cheapest "tiered price" domain?
You either shop around (only if making sure to always read the fine prints as otherwise you may be comparing apples to oranges) or you rely on some website that collects and displays registrars prices... but I am not sure they will handle specific premium prices, as those really depend on the domain name and hence it is near impossible to display in general.
If I transfer between registrars, how do they determine a new renewal price for these domains?
Good question, like for renewals, you can have two cases, paying same price as creation or normal standard one. If the intent between your question is: "let me buy the domain name at the cheapest registrar I can find and then I will transfer it to my most love/preferred/default registrar", I would suggest extreme caution because you may have surprises.
Two ways to counter that:
1. before starting anything, ask your prospective registrar about the operation and its costs; this will also be a good way for you to test their customer service
1. ask the registry directly, their website should give you ways to contact them directly; as they are eager to sell domain names and specifically premium ones, they should take care of answering you correctly and rapidly.
Registrars all seem to have similar domains "tier priced", is there a list somewhere of commonly "tier priced" domains?
See above: most premium cases are indeed handled as groups of domains, but most of the times they are not public.
You can try to contact the relevant registry directly for data, and see what they will answer you.
Going back specifically to .space:
- start by going to https://nic.space, the registry website
- after some browsing you should come to https://get.space/premium-names/ which is registry channel for information and selling of their premium names
- they show examples of premium domain names:
studio.space, cycle.space, dress.space, etc. with buttons to buy them
- for example for one you will arrive at https://domains.get.space/domain-registration/index.php?action=check_availability&txtDomainName=carnival&tld[]=space which clearly shows both the price to buy it and the price to renew it (in that specific case: same one, so the premium price is locked in for all the domain name life); they also put links to "partners", which are registrars selling the name, so you can compare things (the above link is the registry own registrar, it is free to apply whatever price structure it wants, as all registries have to give equal conditions to all registrars, even if the registry owns a registrar - which has the consequence that the registry registrar may not be the cheapest one at the end of the day, or not provide all additional services that another registrar can provide for free or small fee for example, it is just a way for a registry to make sure to have one channel available to sell those domain names, even if they are few registrars selling them)
- and they also specifically provide you a contact form including for premium queries
