i do believe the price hit the 32-bit integer limit.
JavaScript doesn't support 32-bit integers, and the unsigned 32-bit integer limit is only about 4.2 billion. Prices in this game go far higher than that, as I'm sure you know. JavaScript uses IEEE-754 64-bit floating point numbers, for which the maximum value would be about 309 digits long. That would be an impressive price to hit! I wonder what the price was for 3873.