What blade length are you looking for?
The Marttiinni Timberjack is a bit more robust than your typical Mora, and can be found here in the states for ~$15 typically. Its not a especially long blade though (~4in). The Mora Robust/HD is similarly thicker than the normal Mora, and costs about the same as the timberjack. There are longer bladed Moras, but most aren't as thick as it sounds like you're wanting.
Old Hickory knives are all cheap, and they have some larger options (including 7in, 10in, and 14in blade length options). They don't come with sheaths, nor are they very "tactical" in appearance. They are quite tough though, even if the blade stock isn't super thick. They run ~$15-20 or so here.
Schrade makes some pretty good knives for cheap, but most of those are in the $35-40 range, which sounds like its out of your price range.
The Cold Steel GI Tanto is an incredibly tough knife, that around here can be had for $25-30. The Cold Steel Trueflight thrower is also cheap, but less comfortable (again, mostly designed as a throwing knife), that is usually less than $20.
Have you thought about a Machete? Those are incredibly tough, cheap and large. A Tramontina 14in machete chops great, and can baton surprisingly well. They also usually cost less than $15.
Good luck finding something that works for you
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