My worst, I compulsively plopped down $250 on a 3D printed Rey's blaster from Star Wars a few days after seeing the movie.
A few weeks later I saw them on eBay for $50, then later for $25.
Mine is painted up and weathered really nice though, so I can still justify it.
The most expensive props I bought in the past 15 years was a $1200 Tomenosuki Blade Runner Blaster, a $1,000 Richard Colye Blade Runner special edition 1 of 50, (BTW, the Coyle kicks ass way over the Tomenosuki!), a $1,000 Marto Conan Sword, several Master replicas, an AJ Standish E-11 Blaster made from a real Sterling, pre WWII Hengstler counter and a Real WWII M38 scope. I also have some really nice Dstines, Jlong, Brent Jones, Matt White, Cory White, JTK, Matsuo and Roddenberry pieces and other unique one of a kind replicas that I consider priceless!
As it turns out now a days, the majority of my collection is priceless.
I still think the best is yet to come.
You know if your in this hobby as long as I have been, most good things only come around once.
If your not in the right place at the right time, or if you don't have the money, you miss out forever.
I can tell you that almost every good prop replica purchase I have made in 15 years has either held it's value or increased substantially.
I'd much rather have a Dstines alpha communicator than a Terry Reddlin or Thomas Kinkade on the wall any day!
You lose some but you mostly win in this hobby, don't be afraid to spent some cash if you have it or you may be kicking yourself in the ass forever after if you miss out on something big.