I don't get that fractured logic. $10 per month quickly eclipses the retail price.
Take the time to do the math and you'll see how O365 easily eclipses the value of a retail license, especially in the OPs case.
A retail copy of Office 2016 Home and Business is $230 + tax. It can be installed on a single PC at a time, and is transferable.
An Office 365 Home plan costs $10 a month, you get Access and Publisher, 1TB of Onedrive storage, and some Skype minutes thrown in. You can install it on
five PCs, get access to the mobile version of Office (which would be a separate purchase otherwise), have software assurance for a free upgrade to the latest version if it is released during your subscription, and it doesn't matter if you use Windows, Mac, or a combination of the two.
At $10 a month, the break even point is the 23rd month. I don't think
two years qualifies as "quickly eclipsing" anything.
If you have two or more PCs that need Office, you're comparing $230
per device to a flat $230 to cover
five devices.
Installing Office on five devices retail has an upfront cost of
$1150. Again, compared to $10 a month. The break even point on the full five devices is
nine and a half years. That's ignoring the software assurance, if you ever upgrade to a new version of Office in that 9.5 years on those PCs, you just added another 9.5 years to the break even point.
So according to the math, anyone with more than one PC is throwing money down the drain by buying retail Office licenses instead of O365. (There's also a cheaper O365 Home plan we could do the math on, it's like $6 a month but only has one PC license. O365 still works out to be the better value by a long shot as the break even point on $6 is 3.2 years).
Now we get back to the OP, who is specifically struggling with keeping the cost of the PC *with office* below $400. Eating an upfront $230 for the license is totally out of the question, but $10 a month is quite a bit more palatable for someone on a budget.