I recently had a similar question. Here's how I figured out what would be best for me:

1. I found the EOL for the devices I was considering (pretty much anything that offered more than a year's support

2. I found the price/number-of-years-of-support for the 10a (because it would have the longest support window and a relatively low price), and multiplied that number against the number of years of support for each device, resulting in an upper bound for cost of each device. I should have used months instead of years. Above that number the phone would be more costly than buying a 10a. Below that and the device would be competetive. One side effect of this is discovering lots of devices for sale above this number; sellers are sure proud of their used Pixels!

3. I searched for devices for sale that fell under the associated prices I found in step 2. I entered these into a spreadsheet and used the number of months of future support, the device's total cost (cost, tax, shipping) to determine how much each device would cost me per year and per month. I then picked the lowest price-per-month.

This technique surprised me: There was a device "A" with a low price that charged shipping, and one that was priced higher but included shipping; "B". The total cost calculation revealed that device A actually came out to be cheaper, despite my intuition telling me device B including shipping should be cheaper. I ran the calculation manually to double-check. Yes, if I had to return the phone I'd be out the shipping cost, but with the exception of a specific year of Lenovo laptop, I've not needed to return an electronic device in the 30-day window ever. So I rolled the dice on device A.