I reload ...and I still shoot a lot of 9mm ....because I think its a great practice round.
I'm not sure what a "lot of ammo is" .....but since I do reload a premium cartridge using a FMJ jacketed bullet ....my .45 acp reloads run about $ 9.25 for a box of 50 / my 9mm reloads are about $ 5.50 for a box of 50. My hunch is the OP is buying retail ....where .45acp is about $ 20 for a box of 50 / and 9mm is retailing for around $ 12 for a box of 50 ....
But even in my reloads for .45 acp ... $ 900 is only going to give me about 100 boxes ...or 5,000 rounds ...and many of us shoot that much in a year easily in one caliber ...
It might be true / if the OP wants to get into reloading ...he'll like reloading .45 acp ...but if he's going to get into reloading, why not still get a gun chambered in 9mm and then reload 9mm ammo ...and you're $ 900 ammo budget will go almost twice as far.
Most of us that reload / don't really save money we just shoot more ... I was at my local range on Sunday ...with 4 guns ( a 9mm, a .45acp, a .357 mag and a .22 ) ... and 8 boxes of 9mm, 2 boxes of .45 acp, 4 boxes of .357 mag and about 500 rds of .22 .....and had a great day ...and some good practice for under $ 100 probably ..../ both the 9mm and the .45 acp were 5" 1911's / and the .357 mag and the .22 were 4" S&W revolvers ....so drawing and firing the two 1911's was good practice / and so was the .22 and .357 mag revolvers ... same revolver holster / same weight / same trigger pull / same controls ....
so to me, the 9mm is a perfect option ...