This is very much true in my case. When I built my 180g last year, I only ordered a few things from BRS. The bulk of what I ordered came from Amazon.
1. Amazon ships faster and has free shipping(I already have prime). BRS charges me shipping on everything, and it takes them a few days longer on everything. Pay more to wait longer.
2. Amazon has a better selection. While there are a few items that BRS has that Amazon doesn't, for the most part I can get the exact same items from Amazon. At worse it's the same price, but often times it's cheaper due to some individual seller or whatever marking it down. While BRS is always full price. When I bought my Kessils, I saved over $150 by ordering off Amazon vs BRS. Meanwhile, I couldn't even buy my Jabeo return pump off BRS, because apparently even though it's by far the best bang for the buck, BRS is too good for them.
3. I have an amazon credit card which gives me 5% cash back on everything I order. So that $100 item only costs me $95.
Things I actually order and buy from BRS:
All my dry rock, marco, the cheap stuff.
Super glue - I love their big bottle of superglue.
Marco Cement - probably could have gotten it elsewhere, but I was already ordering everything else.
7 stage RODI system - I bought a cheaper one off Amazon 2 years ago, the BRS one is much better.
All my dosing additives. Can't beat BRS for these from what I've seen. I dose the 2 part and also the tropic marin 3 part system.
And that is it. I found better deals and/or products they don't carry elsewhere - mostly on Amazon.