You lose the warranty if you don't do the service.
At least here the practice of requiring servicing at the manufacturer's own dealership is deemed illegal, and warranty can't be void if the service is done per the manufacturer's requirements and correctly, at any provider who are equipped to do it, and trying to prevent it is also illegal.
Same in Australia.
Speaking of vehicle costs; I did some back-of-the-napkin maths a few years ago when I bought my current vehicle. For me, overall, it was cheaper to buy a fairly economical turbo-charged ICE car, than an EV of similar quality/spec. Depending on the time of year and the manufacturer, you can get yourself free or fixed-price servicing in the first handful of years. The insurance was also a huge expense. Currently, I pay about $860/yr for comprehensive insurance, with an agreed value (not market value) on my vehicle. It also includes 1 free windscreen repair/replacement each year, that doesn't impact my premium or claim-free standing. My insurer wouldn't even offer insurance on a Tesla. Some of the other quotes I got for a Tesla 3 were at least quadruple my yearly premium and probably then some. My insurer isn't some small, budget company either, it's a fairly well known brand.
Coupled with range issues (I do travel quite a long distance on freeways), the cost of fast chargers, etc... The maths just didn't make sense.
In Australia, in the states I live/drive in, every single petrol station has live fuel pricing through an application (run by the state government) on my phone. Personally, I deem half a tank to be "empty" and I'll start looking for places to fill up, depending on my movements. This gives me plenty of buffer to wait until the prices are low, or I can find somewhere along my planned route to fill up. It's not unusual to save something like 20c per litre on 98RON fuel just by not filling up at my local service stations, and planning ahead a little bit. For example, right now, looking at the stations I've favourited along my most commonly travelled routes, they range from 191.5 cents through to 222.9 cents per litre for 98RON unleaded. Lowest in the state is currently 171.5c/litre, highest is 259.0c/litre (neither are anywhere near me).
Also speaking of fuel, since I know some people are playing along at home, the lows/highs for various fuels in my state (New South Wales, Australia), at time of writing, are as follows:
E10: 149.5 to 213.9 cents per litre
E85: 209.9 to 221.9 cents per litre
91RON: 151.5 to 256.9 cents per litre
95RON: 167.5 to 259.9 cents per litre
98RON: 171.5 to 259.0 cents per litre
Diesel: 162.5 to 269.9 cents per litre
Biodiesel (20%): 245.0 to 249.9 cents per litre
LPG: 89.9 to 149.9 cents per litre