I don't think any of the answers here are really going to be much help for you estimating your own travel budget - because everyone is different and travel differently.
On a typical year where I'm working full-time, I might go on 1 - 2 interstate trips and spend anything from a few hundred to maybe about a thousand, or I might go on an overseas trip and spend around $1500 - $2000.
Last year was an anomaly for me because I actually spent 5.5 months outside of Australia in total (Nepal, Malaysia, Myanmar, Thailand, Taiwan). I could probably gather all my expenditures to give the most accurate figure, but a lazy guesstimate is that I spent about $7500 AUD (or $6070 USD) for all of that, inclusive of everything (flights, visas, vaccinations, travel insurance, accommodation, food, activities, miscellaneous).
Above costs are for just for me, one person - but I travel with my boyfriend (we have separate finances which is why I'm only counting my expenditure) so I usually benefit from economies of scale in regards to accommodation.
We make our travel choices based on what's affordable and what's interesting. As long as a destination meets the two criteria, they're up for consideration. Then once we're there, we make decisions based on our priorities. As with anything else, it all comes down to what you feel is worth spending on.