On-Ramp/Off-Ramp Liquidity Providers and Fees for DeFi Operations

Anyone else finding it a constant battle to manage fiat on/off-ramps for larger DeFi operations? The spread slippage combined with various platform fees from different providers just eats into alpha. We're looking at moving decent size chunks, not retail crypto buys. The biggest headache is the inconsistent liquidity and the opaque fee structures once you're past the advertised rates. What's your experience been trying to find reliable institutional-grade liquidity providers for stablecoin conversions? Are there any that don't absolutely scalp you on larger orders, or is it just the cost of doing business in this space for now?