Talking of most expensive purchase,this my Wrenn Royal Scot which i bought a few weeks ago & converted to 3 rail hauling a rake of refinished Trix Mk1 coaches.
Whilst on the Trix theme, I thought you may be interested in my Transpennine unit running on my HD 3 rail layout.
A Wrenn Spamcan converted to 3 rail using a Marklin skate.Clearances are very limited on these locos,you can`t fit a Hornby dublo collector unit unless you alter the chassis.I do have two of these locos.
A modern Hornby 2BIL converted with a Marklin skate under the trailer car & power fed through to the power car via a plug & socket.I do have photos of all my conversions but i can`t post them on here.
A Hornby 9F railroad loco drive since modified with a Dublo 8f 3 rail tender
And finally for now,an Airfix tender drive Royal Scot with a Marklin skate under the loco.Sorry about the radio,i forgot to turn it off!!.