I think the pools have been stabilized with their payouts for, let's say half their lifetime now, so we're dealing with about a 75% of 50% of 97.6% of 90% of 10315, or about 1132 bytes, which is only about 51% larger than fluffypony explained.
The original pool payouts were absolutely terrible, but even after the dust fix they can still be quite small, paying out as little 0.1-0.3, which is something like 4 USD cents. That creates an excess of small outputs on the chain and makes subsequent transctions larger too.
Unless we expect Monero to be used for microtransactions in a big way, the mix will change once mining and trading of recently-mined coins is a much smaller proportion of usage.
I see that it's not getting bigger, but please, understand that this is a massive number.
In terms of storage on your computer, it is not. A moderate 1 TB hard drive costs about 60 USD so a 3 GB file costs you about 18 USD cents. A 100 GB SSD is about the same, so 1.80 USD. If you don't think running Monero is worth 0.18-1.80 USD (a one time cost that you can recover by uninstalling it) to you then I guess its kind of a waste of time to even discuss.