I remember years back , I worked at a gun shop , that specialized in higher end firearms/knives/gear. I was not into knives at the time , all I knew is we had about 10-15 Mad Dog knives at any time , at the shop I can't ever remember selling one , but at larger shows like SAR or SOF , they always sold.
You have a dedicated group who are steadfast on MD knives.
You also have those that are steadfast on Strider ( like me ) , Busse ( never owned one , but think highly of Jerry ) , as well as others like RAT , TOPS , etc.
Best thing to do is do your research , set your pricepoint , handle whatever you can that you are interested in ( not as easy as it sounds I know ) , then make your decision.
I found them to be well made knives , but not worth the price to me. It is obvious they are worth it to those who like them as they sell fast on the secondary.
Now these could be collectors buying for a resale later , or they could be someone who just wants one and will pay the market rate to get one.
Personally I don't care for the maker himself , his knives although well made , don't overshadow his attitude and " everyone else sucks personality ".
If you want to know about the MD , PM or Email Parker here on the forums , he knows a great deal about them , and while he is a MD fan , he will also give you the straight and narrow on what may work for you , and he might even be able to toss you a lead on a few.