For an owner operator, an R22 and maybe an R44 would be able to do SF to Lake Tahoe for well under $250. For a charter service you could probably get a commercial operator to do it for maybe around ~$500 and there are definitely some inefficiencies you could remove there. Lilium is on crack if they actually think $250 is going to be the all in cost for a private flight though. You don't just spin up a new air frame and 135 operation and make money at those numbers...unless you pull an Uber on steroids and open the VC floodgates...