On-Ramp Fees for Larger BTC Transfers

Anyone else finding that the 'fixed' fee structures for on-ramping into BTC are actually just a facade once you hit certain notional amounts? I've been trying to move a decent chunk over the last few weeks and what I'm being quoted by my usual channels, which are supposedly low-cost, are just not adding up. It's almost like they're building in a spread on top of the published network fees, or maybe their liquidity providers are charging them more. Makes you wonder if it's worth shopping around more aggressively or if this is just the new normal for anything above, say, $50k. The smaller guys seem to get a better deal percentage-wise.