Are you getting confused between registry and registrar?
There is only one registry per TLD (and this applies to both ccTLDs and GTLDs). If you resell directly for the registry then you are a registrar - regardless of what the registry chooses to call you (some registries use different terms, such as "registration partner"). If you resell for a registrar you are a reseller.
As for prices - some ccTLDs are more expensive than others, for whatever reason. It could be that they are not fully automated - so there is more manual input, hence higher staff costs. If they are a small registry serving a small community (such as many small island states) their overheads per domain are necessarily higher. If they work in a restrictive environment (e.g., in a country where all registrations have to be approved by the government) then that, too, will mean higher prices.
Yes, there is only 1 registry per TLD, ie 1 for .com, 1 for .ca, 1 for .us...
The Registry manages the TLD database and it would be a total mess if more than one entity did this. In most countries the Registry sells to Registrars (ie Godaddy, Enom) who sell to end users. It appears that the .ph registry provides both registry and registrar functions..and sells to registrars and end users.