Answering your questions in a logical order:
Google probably paid $10/year for their domain name. Yes, it's probably a similar price.
You own your domain name. If your registrar said "it's going to cost you $1000 to renew" then they will go out of business, because you can transfer it to someone else who will charge you less. (Transferring around the time of renewal is a complex topic I'm not going into.) If the registrar does something wrong then you can appeal to the organisation that looks after that Top Level Domain. For example, it's a different organisation that looks after .com compare to, say, .uk. As they have ultimate control over domains they can put it right.
Provided you keep renewing it then no-one can take it away from you. Even if you forget to pay on time there is a short period where you can still renew and not lose it. See this question: How long is the redemption period on a domain?.
One thing to make sure is that if you change email address or postal address then you tell your registrar so they can still contact you for renewal.