The advertised prices are complete bullshit. Every vendor shows you these clean monthly costs assuming everything works perfectly, your data is pristine, and you never encounter edge cases. Reality? I've never seen a migration finish on budget or on time.
The Real Cost Breakdown (From Someone Who's Been There)
AWS DMS looks cheap until you actually use it. They charge like 10-20 cents per GB monthly for storage, plus compute hours, plus cross-AZ transfer fees, plus all the AWS services you need to make it actually work. That VPC endpoint? Around $7-8/month. NAT gateway because their networking is fucked? Like $45/month. Enhanced monitoring because their default logs are useless? More money.
I spent 3 weeks debugging "Error: An error occurred" messages from AWS DMS. Turns out it was silently failing on a single Unicode character in our customer names table. Their documentation mentions none of this shit.
Fivetran works great until they count your data. Their MAR pricing sounds reasonable until you realize they count every nested JSON object as separate rows. Our e-commerce product catalog went from 100K rows to like 3.2M "monthly active rows" because each product had variant data stored as JSON. Suddenly our $15K/month estimate became almost $50K/month.
The sales team was pushy as hell and kept promising discounts that never showed up. After their March 2025 pricing change eliminated account-level discounts, costs jumped like 60% overnight.
Stitch Data is the least likely to fuck you over with their straightforward $100-$1,250 monthly tiers. But their row counting is still weird - nested JSON data inflates counts unpredictably. At least they're honest about it in their docs.
Implementation costs are where they really get you. That "2-4 week enterprise migration" timeline? Complete fantasy. Every enterprise migration I've touched takes like 3-6 months minimum. Schema conversion tools help with the obvious stuff but break on edge cases that require weeks of manual fixes.
Budget $50K-$150K in engineering time, not the $15K-$30K they tell you. This assumes your team already knows the tools - if they don't, add another $20K-$40K for training and the inevitable learning mistakes.
The Gotchas That Will Destroy Your Budget
Data transfer costs sneak up on you. AWS doesn't just hit you with storage costs - they also charge for cross-region transfers, VPC endpoint traffic, and bandwidth overages. We got hit with like a $3K surprise bill because our migration was pulling data from us-east-1 to us-west-2. Nobody mentioned this during the sales calls.
Enterprise features cost 2-3x more and you'll need them. Fivetran's Business Critical plan costs over double their standard rates, but good luck explaining to your CISO why you're not using customer-managed encryption keys or private networking. Every compliance requirement adds zeros to your bill.
Custom connectors and transformations will eat you alive. That legacy ERP system from 2003? None of these tools support it out of the box. Stitch Data uses the Singer framework which sounds great until you realize building a custom Singer tap takes 2-3 engineers like 6 weeks minimum. Budget $60K-$120K per custom connector.
Performance scaling is exponentially expensive. Our migration started hitting timeout errors at scale, so we had to bump AWS DMS from 1 DCU to 8 DCUs. Costs jumped 8x overnight. Fivetran's MAR-based pricing means more data equals exponentially higher bills - there's no volume discount that actually helps.
Support costs real money when shit breaks. Standard support is useless when your production migration fails at 3am. Premium support contracts add like 20-30% to your annual costs, but you'll pay it after the first time you're on hold for 4 hours while data piles up in your source systems.
The real TCO is always like 3x the initial estimate. Budget accordingly or prepare to explain to your CFO why the "simple migration project" just burned through your entire Q4 budget.
The disconnect between vendor promises and reality is so consistent across the industry that it's worth laying out exactly what they tell you versus what actually happens in production.