To be fair, that's billions in revenue, not profit, so I wouldn't say they "make" a couple billion per year. In fact, the source you linked to shows that their operating income is negative, so after subtracting expenses from that revenue they are losing money. So, they don't have a few billion in spare cash sloshing around -- that $2.6 million is not a negligible amount of money for them. The fact that they still think it is worth spending on lobbying when they don't have a lot of spare money is perhaps an even stronger statement about how effective lobbying dollars are.