Musk's problem isn't so much the massive figure, but the mathematics behind it. The $4.9 billion adds together the amount of subsidies for the three companies going back about a decade. In the case of Nevada's $1.2 billion incentives for the Gigafactory, they're even amortized over 20 years into the future. Treating the total as a lump sum is unfair in the CEO's opinion.
Also, not all of this money was necessarily earmarked for the three businesses or even came from taxpayers. For example, the $4.9 billion includes tax subsidies or rebates to buyers of zero-emissions vehicles and solar cells, but the same incentives would have applied to these products if someone had bought them from a different company. In addition, the LA Times accounts for $517 million from selling ZEV credits, but Musk argues that those funds came from other automakers rather than the government.
According to Musk, the only government incentives that his companies have directly bid for were the state-level ones like in Nevada for the Gigafactory and in Texas for SpaceX. He also stressed that while this money was helpful for them, the subsidies weren't necessary to keep the businesses going. The entire 13-minute CNBC interview can be watched below.