Electricity is much cheaper than gas, anywhere from 1/4 to 1/10 the cost depending on your service. Check your utility bill for current cost per kWh (usually $0.10 - $0.20) and multiply by 80 (current 3/Y have 82kWh batteries) to figure the cost of driving 300 miles. Most utility companies offer EV plans for even lower costs if you charge at night.
You do trade some quality for technology of course. Many of Tesla's unique features and styling are actually clever cost-cutting tricks (e.g. using your phone as the key), while others are simply cheap (e.g. lousy panel gaps/alignment). Where BMW lets you choose which color thread you want your seats stitched with, Tesla doesn't even offer sunroofs. They are masters at cost cutting and they use those savings to deliver a powertrain that is superior to everything else on the market.
They are also masters of growth. By eliminating nearly every branch of customer service and making almost no effort to deliver cars in flawless condition they can focus their resources on new factories and production methods. This gives them terrible ratings in every initial quality survey but that's fine with them since they don't need to attract customers right now, they need to build factories.
As for range, you can go about 4 hours on the highway before needing to recharge. That probably covers nearly 100% of anyone's needs. Yeah, we all remember that one time in college when we drove for 5 hours or maybe even 10 for some reason. If you're still doing that and don't want to do it in the other car, then yeah, you'll have to stop for an hour and recharge at one of the countless fast chargers on your route.
If you're torn between 3/Y and coming from a big ol' X3 I'm sure you know the Y will be more familiar. It's also a much newer design and a bit more refined in my opinion. The doors close nicely, the windows seal nicely, the trunk is fully finished, the rear seats fold at the press of a button, the frunk is of usable size, and of course the cargo/passenger capacity is exceptional. I'd never trade my 3 for one though.