The only reliable source for semi-accurate item prices is JellyNeo, but the freshness of that data depends on the frequency of your queries. JellyNeo allows for approximately five hundred page requests per day without temporarily banning you based on your IP, assuming that the amount of page requests that you're performing appear to be done at human speed. Slightly more page requests after the temporary ban won't do any harm, but if your subsequent page requests number in the thousands, then they'll permanently ban your IP. They'll also ban you outright if you're slamming their server with too many page requests in a short period of time. You can get fancy with proxies in order to spread out your traffic and avoid or circumvent bans, but there isn't a better or faster option than JellyNeo when it comes to mass pricing. Always code your solution to run at a trickle to avoid drawing attention to yourself from either the Neopets or JellyNeo flagging mechanics.