Picton's lifeblood is the constant movement of visitors through the town as they arrive or depart on the Ferry. A consequence of this is the prices which tend to be on the high side. On a positive note you can get a few bargains as the declining number of visitors results in many stores having a few 'specials' to get people in through their doors.
Food is generally priced on the higher end but you can still get a cheap meal if you are okay with fish & chips (eg at Kiwi - see my food tip) or similar.
If you're doing the Queen Charlotte Trek, avoid to stay at the Furneaux Lodge. At least the backpacker's section is just a shabby and dirty dump. They charge you 25NZ$ for a bed plus an additional 2$ for the shower!
Fun Alternatives: Better take a tent instead!
On the occasion of bad weather in the Strait the Inter Islander cannot cross the Strait to and from Wellington to Picton so there are many passengers stranded in Picton till the weather subsides. Accommodation can be difficult till the backlog of passengers is cleared.
Unique Suggestions: Book in advance if you have to overnight in Picton
Fun Alternatives: Take a tent