Bell used high prices on long distance to subsidize low prices for service. Their reasoning is that if Mr Rich Businessman wanted to pay top dollar to call grandma, they wanted grandma to be hooked up.
After Bell split, in the short run long distance prices remained fairly high, and local carriers increased prices 10-fold. The inevitable war in long distance prices that you're thinking of didn't really get going until the 1990s.
As for Standard Oil, http://www.economist.com/node/347251 claims that it was worth far more in pieces than together. the best figures that I can find are these. At the end of the year when it was split, the pieces were worth about $600 million. Over the next decade they wound up paying out $900 million in dividends and still wound up at a combined value of $2.9 billion. (See https://www.fool.com/investing/general/2013/05/15/the-day-bi... for a source.)
Prices rapidly declined after the Bell breakup. And the Standard Oil monopoly had a clear negative impact on all manner of prices thanks to the manipulation of rail freight.