In order to offer high quality services, VPN providers have to pay considerable amount for the bandwidth and it makes it hard to find a reliable service with low price.
While you search for low cost VPN service please note that very cheap VPN Providers are more likely to log your activities and serve contextual ads while you're connected. They're also more likely to use your usage habits to tailor future ads to you, have fewer exit locations, and weak commitments to privacy so if logging and privacy are important to you, you may want to avoid them.
In regards to Japanese VPN , I remember Purevpn.com has a server in Tokyo with a reasonable price (I tried it once and it was satisfying) however you might find other reliable vendors offering Japanese IPs if you google for it.