Caramelization is a mix of dehydration and sugar conversion. I've found that slicing thinner helps the dehydration process go quite a bit faster. Sugar conversion seems to depend on batch size (more onions = more time).
I suspect two things are going on.
The first is temperature. You can start low and go slow or you can start hotter and decrease the temp as you go to avoid charring. Actively controlling the temperature is faster, but increases the risk of accidental charring.
The second is your target state. You and the prior poster might just have different stopping targets. I personally keep going until it's nearly impossible to avoid charring and that takes me... quite a bit of time. By this point sugar content and flavor is maximized and highly concentrated. There's also a very substantial mass reduction thanks to evaporation.


You're going to have a hard time beating $2/mo unless you roll it into something else like blackblaze ($100/year for unlimited storage), Microsoft office 365 ($100/year with 1 TB of OneDrive), etc. If your space is going to photos, the speed and responsiveness of Google photos far outpaces some of the alternatives (cough cough OneDrive).
Self hosting is a viable alternative if you're interested in having more control/local storage or if you are interested in this kind of thing and want to do it/dabble in it as a hobby.
I personally built a NAS, which will take far too long to amortize vs just paying $2/mo. I chose this route because I value a local backup and because a NAS can a bit of a lifestyle product. "It can double as a server!". Sounds fun, but I would want to build the thing I host which will also take time so... You could potentially build a NAS that will average out to $2 or less a month if you have spare parts or score some used parts cheap. Odds are that route could also be used for self hosting.