They are not as heavy duty as a good 3 point disc setup and they also won't spread lime. You can buy a brand new 4-5' disc for $500 or so, a slightly used York rake for a few hundred, a good tow behind drop spreader from Northern Tool for $200 that will do fertilizer and lime,build yourself a drag to cover the seed for next to nothing using a section of chain link fence, andyou can spread your seed with a hand seeder.
This is what I've beendoing for my 4th year ofplots and what will be over 3 acres this season, and it's working fine and I saved a
LOT of money over a Plotmaster. This is alsoMUCH less prone to expensive maintenance or things breakingwhen compared tosomething like a plotmaster that has tons of moving parts.
A few pics of the tools I'm using, the york rake (not pictured) and the disc are towed behind a 29 horse Kubota 4WD, and the drop spreader and drag are towed behind a small 12.5hp Simplicity lawn tractor. You can see me spreading lime in the second pic, and the third pic has the spreader with the homemade drag attachement behind it.