Costs
The strength of the US Dollar will make perhaps the biggest difference to foreign visitors, but even then Austin is, by regional and global standards, fairly expensive.
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At the budget end (staying in hostels, rarely eating out, walking and visiting mostly free sights), you might be able to get away with about $100/person/day.
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A more average budget for most visitors (staying at standard hotels or B&Bs, eating out once a day, going to the full range of sights and taking public transport), would be around double that, at $200/person/day.
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Double that again and $400/person/day buys a pretty luxury experience, with smart hotels, meals at the full range of restaurants and taking taxis around town whenever you feel like it.
Note that traveling solo will probably raise any of these per-person-costs by at least a third for all except budget travellers.