You don't know anyone that buys large HotWheel collections do you? I have about 30K of them still in packages.
Most of the guys who come to the local shows wouldn't have the funds or room to handle that much at one time....
They're either middle aged people who are beginning to cull from their collection and trying to downsize, or younger guys who are just bringing and buying/trading the new hot stuff, hoping to get rid of it while they can still make maximum return. There are a few big dealers in the greater Houston area, and they mainly come to the larger swap meets (like the ones in Conroe in October and February). I haven't been to the DFW area in 13 years so I don't know what the scene is up there. There's more swap meets there though.....
Might be worth going to some of them, with some pictures and descriptions of what you have, and see who's there and talk to them.
The one guy I know here who has the $$$ to buy larger collections, will lowball you big-time. He's tried to get a pretty large collection that a friend of mine is trying to downsize (he's retiring and moving to his lake property and doesn't have room for everything he's amassed in 40 years) and wanted to give him pennies on the dollar for it. I've been evaluating and inventorying it for him, and he's letting me sell some of it (with compensation!).
The Hot Wheels that hold their value best are the original redlines from '67-71, and the mid and later 70s stuff is still fairly good value wise. Of course condition is very important; a rare car on a bad card is worth half, or less than half, of the same car on a nice card. First series Treasure Hunts are bringing some $$$ particularly the Camaro and VW Bug. The VW Bug is a $500 car at least, on a mint card. 80s and early 90s stuff is bring $5 to $20 a car; Ferrari and Lamborghini cars are on the high end of the scale.
There are exceptions; the yellow Chevy pickup with Real Riders vinyl tires in this picture, is a 3 pack exclusive and the last time I checked, was being offered for $75-100 online. Online prices fluctuate like crazy though so that's not the best way to gauge values.....