i recently needed a large-ish midi keyboard so i bought a dsi rev2, since, ya know, it has a large-ish keyboard AND a complete synth. i actually SAVED money. right? 
years ago i bought an early ipod but my computer at the time didnāt have enough HD space to accommodate the device. so i bought a new mac.
āthereās a gap on my desk and itās shaped conveniently like a synthā
I have an empty wall behind me, perfect fit for a midsized modular.
My Co-worker told me it was ok to buy the Rytm because she used so much money on golf gear
I have a really small setup, but all MKl devices became really affordable these days - my actual real existing problem 
haha that checks
I have a new table for some synths setup against the studio back wall. Canāt be bothered with long cabling so why not get another set of monitors instead.
I have 5 synths that I never use.
So, I should buy 5 new ones that I actually will use.
āProduct X in this youtube video from Y looks like fun, sounds warm, does something no other of my devices can do and letās me produce good tracks instantly. Ok letās seeā¦ how much is it? Damn! Ok I could sellā¦ no I canāt let this one go and I also need it forā¦ AH DAMN IT NOT AGAIN!!..but maybeā¦ā
I bought stuff because I wanted it , not because I needed it.
But that was last year.
This year Iām selling it because I havenāt used it.
I wanted another red synth that went bleep ?
ā¦ I have too much nord ā¦ if thatās possible.
Meta-justification:
My soundcards only has 8 inputs. I need to buy a new soundcard with more input so I can plug more synths. That I donāt have. Yet.
The one that has gotten me more than a few occasions of late has been the really tempting second hand prices that folk tend to advertise things on here forā¦ Iām scared to look at my posting history as itāll primarily be posts in the sellers feedback saying āgood and friendly transactionāā¦
Iāll buy it now to save myself the bother of buying it later.
I am lucky enough to have a rack of 64 converters. I need to fill it with stuff!
āBuy cheap, buy twiceā is one of my favourites.
Almost did the REV2 thing last weekend but I opted for a Novation 61SL MKIII and decided to opt for a REV2-Desktop. That way, I wonāt damage the keyboard of the Prophet by playing it!
Economically sound decisions!
Smart amiright?
ā<this device> is the only one iām yet missing to create music of my dreamsā.
every time
That one is actually true tho!
I am on my 3rd interface, had I bought apollo right off the bat Iād been good all along!