Yeah, cheap laptops are cheaper than 600-700. Sound shouldn't require a ton of horsepower, so you could get something new decent at that price. ThinkPads, HP (business line), Dell (business line) are the usual recommendations. Wirecutter tends to have good suggestions too.
(I think all new Chromebooks can run Linux applications now. So that'd be a way to run Audacity. But that would only make sense on much tighter budgets.)