OMG centralization

20 MB blocks mean that a non-mining full node needs ~270 kbit/s downstream. Since you also want control traffic, tx's that get sent to you outside of blocks, ... make that 1 Mbit/s. If you can watch Netflix on your device without puking pixels, you can run a full node.

Now, upstream for miners is a bit more difficult. If you want to reduce the risk of your block being orphaned, you want to push it out fast. If you want less than a 1% chance of someone else mining a block while you upload yours, that would be 100 times as much, so ~ 30 Mbit. Let's make that 150 so you can upload your block to five people at the same time. That costs you around seven bucks a month. This is, of course, assuming you don't use a mining pool anyways, which you likely will if you're small enough to worry about things like that. Or you can simply mine empty blocks, if that's what you choose to do. Then your additional outbound bandwidth requirements are 0.

Coincidentally, one such box will also supply the required bandwidth to feed 200+ full nodes during the 99.99+% of the time where you aren't uploading your block.