Crazydomains renewal price for .net is 8,80$, Cloudflare charges more than a dollar more each year.
Crazydomains charges 7,20$ for .com renewal, why is Cloudflare more expensive again?
You are also more expensive than reputable providers like porkbun.
I thought there was no markup?
Cloudflare’s pricing for .net seems to be a bit off. They claim it is $9.77, when it appears to be $9.02 (both excluding the ICANN fee).
For .com however the pricing seems to be accurate. Your example with Crazydomains does not seem to be entirely correct as they charge $9 per domain.
(begin theory)
As for why it’s 77 cents, maybe the price isn’t flat, but instead, the amount is based on when the registrar contract is signed.
Verisign (initially) knew October was when Cloudflare would open the registrar business.
The month of October is 83% of the year done.
since the price increases 10% yearly, $0.902 would be added to the price upon the date of February 2019.
83% of $0.902 is ~$0.75
$9.02 + $0.75 = $9.77
(end theory)
^The above is probably not how it’s actually calculated but shrug.
As for why/how other registrars have cheap prices, many of then take the blow for the cost up-front for the initial registration (like how GoDaddy can offer new customers .com for $1) but then they make it back by doing something like charging higher renewal rates, pushing their other services (hosting, email), etc.
Cloudflare doesn’t making any money off of registration/renewal by hoping that you’ll upgrade the domain to the premium plan in the future.
A good theory, though I am not buying it 
Most registrars and their offers are blatant rip-offs. Yes I am talking about you, Godaddy and Network Solutions. Even Namecheap hasnt been living up to its name for a very very long time.
Verisign has a strange arrangement with ICANN in that they also breakout the ICANN fee embedded in their cost, unlike for .com, full details here:
https://www.icann.org/sites/default/files/tlds/net/net-fees-01feb18-en.pdf
It’s definitely confusing - that $0.75 is the ICANN fee that Verisign as the registry pays ICANN. The $0.18 is the ICANN fee that we as the registrar pay ICANN.
Is there an overview of actual costs per domain for registrars somewhere?
Today I’ve noticed that I could finally transfer my .io domain to CF but then noticed that CF would charge me over 10$ more than the current registrar. The registrar the domain is currently managed by charges 2$ more each year for renewal, whois guard is always free. At that rate it’d take over 6 years from now for CF to be cheaper and 13 years for the other registrar to make a single penny off my domain. Even if the price the other registrar charges me doubled for every renewal, they’d still have provided me with a domain with net loss on their side for 3 years.
Not accusing anyone telling lies, but it does sound strange.
Best site I can recommend: https://tld-list.com, but ya, see the thread posted by @shimi. io is a cctld so they may have different pricing policies.