Whether you paid too much is largely in the eyes of the beholder. Pretty sweet -looking terr in any event.

In its current locale, the plants therein will likely not receive sufficient light to prevent etiolation without supplemental lighting.

Are the inside joins well sealed? If not, than issues with the metal "rusting"/oxidizing will exist.

How airtight is it? Without air circulation, molds/fungi will likely be an issue.

How often to water depends on a host of factors including: air circulation, temps, type of media, types of plants, and number of plants.

Do keep in mind that the situation gets far more complex if/when animals are introduced to the setup. I would highly recommend you nix any idea to include "wildlife" until you master caring for the terr with just plants.

You do have quite a bit of a learning curve ahead of you -- particularly if this should be your first terr. However, I don't see that it should be insurmountable. It'll just take some time and dedication.

Do you think it'll hold water? If that's the case it can definitely be converted to house some small species of frog or maybe an anole or two, but I wouldn't recommend it in its current setup. Maybe some humidity-tolerant insects. It would be a really rad setup for some mantids, but you'd need a screen to cover the opening and still allow good circulation. Some springtails and Isopoda would help keep the soil clean and active. Good luck!

I see succulents in there. My understanding is to wait for the soil to completely dry out before watering. Usually takes 1-2 weeks in an open container, might take longer in this one.

If adding lizards, you will need to completely tailor the environment to them. Depending on what you get, you may need to replace some plants in there and add some lighting/heat for the lizard.

Really nice purchase by the way!