I'm new to Azure platform and pricing. I want to build a small mobile application targeting various mobile OS platforms.
Is it wise to get a SQL Azure or host my WCF service somewhere else based on the pricing?
If you recommend SQL Azure is the Pay-As-You-Go well enough to handle the app?
To be honest your question is quite vague, and I dont think there is an absolute right answer based on the information you have given. Your going to need to assess your requirements with the database offerings and decide what you need.
If things like load balancing, transparent failover and other cloud features pique your interest- Azure may be the correct choice. Otherwise SQL Server or other 'traditional/non-cloud' SQL DB implementations may be the way to go.
In terms of cost, here are a couple of comparisons, but again it comes down to your application specifics.