Spending $700 per month on your work tools (where that represents 2-3% of revenue) is not unreasonable. My minuscule office space in the shitty part of town costs as much.
I think anyone running their small business that depends on high performance computers should have an annual budget of at least 1% of revenue for hardware.
You can justify it to yourself however you like, but outside of your bubble, it's a poor allocation of money.
The alternative is like feeding an animal instead of letting it live the lifestyle it's adapted for. That helps it in the moment but over time its capacities atrophy and it ends up weakened, twisted and harmed with nothing to spend its natural instincts on.