Spending 1% of your net annual salary on a laptop still strikes me as a large purchase.

There is a world out there where people pay 15~20% of their annual income to buy a computer

seen under a different lens: you think that an effort a person does over 3.65 days to afford a computer is expensive, while many people would have to accumulate the effort of 73 days to afford it.

You're buying a tool for your work, it will last at least 2 years, and as a developer you have almost no ongoing costs or required consumables. Comparing to many other kinds of jobs, 1% per year for equipment is nothing. If it makes your job more comfortable or faster, thinking too much to decide between 0-2% of your annual salary seems counterproductive.

large: yes, justifiable: very possibly.

I think of a laptop in the same way as a chef's knife: it needs to be an extension of your being when you are in the zone, and good tools do that. Ive had near-religious experiences woodworking with good tools and other craft types tell me they have too.

for such a tool, 1% is nothing.

A large purchase- but perhaps just small enough you can agree with yourself to let go of worry. Perpetual anxiety about theft is no way to live.

What if one only buys a laptop once every three or four years? Then it would be 1/3 or 1/4 of a percent of annual salary.

It would probably be tax deductible, depending of course on variables not discussed yet.

And the worldwide percentage of laptop users and devs that make 150k is how much?

As long as you have backups

Even if you knew that it would never get stolen the SSD could still die unexpectedly. Or any number of other problems.

Having anything local is reckless at this point imo. There are so many mainstream backup options at different price ranges/free!