I am to a point. each exchange API has different keys and such. I may just stick to using the 5 or 6 high volume exchanges, it'll be relatively accurate.

Thanks. That is how I have been going about it but it's quite time consuming. Maybe that's why they charge for the data afterwards.

@David But why does the value of BTC in USD change per currency pair? I'm not understanding what factor determines the slight variation in USD per currency pair.

Look at coinmarketcap.com/currencies/bitcoin/#markets ...the value of BTC in USD changes per currency pair. I'm having a hard time figuring out how they determine the value of the base currency, in this case BTC, from a trading pair in USD or any currency for that matter.