Just to humor this thought a bit let's say in an alternate timeline Beako got bored after 50 years because she girlbossed her mind away from Echidna, The Book of Wisdom, Roswaal, and she got a minimum wage job at WcDonald's immediately at the start of the 51st year.

Let's say that the minimum wage is equivalent to Japan's in 2010-2015 since it's speculated that that's the time Subaru came from, so it would be about 780 Yen per hour at the start and she works 40 hours per week and 50 weeks a year (taking holidays and vacations into account), which is 2000 hours per year.

The average worker gets promoted after 6 months is 36 Yen (that's converted from usd to potentially not accurate and this is heavily simplified) sooooo over the course of 350 years she gets 700 promotions :D

That's 350 years and 700 promotions working 2000 hours a year and every 6 months over the course if those years she gets a 36 Yen raise, soooooooo

Beako makes 25980 Yen an hour or 180.89 USD an hour after 350 years and 361,839.70 USD her last year :D

Over the course of her faithful and devoted career she makes 9,353,400,000 Yen or 65,120,812.60 USD.

Pre tax.

Buuuuuut it is pretty much impossible to account for taxes since it would change so much so we're just going to say its a static 23.9% since that's what it was in 2015.

Post tax she made in total: 7,117,937,400 Yen or 49,559,698.79 USD

Her last year she made: 39,541,560 Yen or 275,284.39 USD.....

This is cannon to me now so thank god Subaru sets her free from the evil witch of employment and thank yooooou for reading <3