They do it to get under the new lower tax rebate limits for cars. Luxury cars are (rightly) getting less tax breaks than they used to. And Tesla is lowering prices to make sure their customers still get the rebates (which is still a huge reason anyone buys electric cars at this stage).

The irony is that Muskrat was railing against rebates and wanted them to be cancelled, but when sensible lowering of limits made his cars uncompetitive, he could magically lower the price to keep the competitive.