[gumpzilla]

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I thought I might have a better hand, but if so I didn't expect a call. . . . But then I'm losing fold equity from, say, a better seven or pocket 8s or 9s.

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At a low buyin tournament, I think 8s or 9s are almost never going to get away on this river. There's not much reason to think you have a T or an overpair (some people will check JJ in the BB there when it gets to them, but not so much at low buyins.) The only hand to be scared of is trips, and since you led before those got there I think you won't be taken seriously on that front either. Better sevens may fold, that's pretty opponent dependent.

In a nutshell, I think against most opponents you'll have a hard time folding better hands and will get called extremely rarely with worse hands. So betting seems likely on balance to be a losing proposition. If you think your hand is probably best, I prefer check-calling in this spot; that way you can at least hope to get more money in from worse hands here more reliably.