Yes. Roughly triple the cost per mile over time and you have to have $10k in the bank that causes you zero pain or emotion when it leaves suddenly. Don’t forget that any tows start at $200/hr port to port in an HDT too.
You can DIY some stuff but like others have said, you need tools bigger than your 1/2” impact to work on them and you can remove a finger in a HURRY if you aren’t careful. I do some small stuff but I’ve found it’s just worth my time to have the shop do things for me since they are just faster and better at stuff like brakes and suspension.
Parts costs are an absolute killer as well. I’ve lost a couple turbos in my fleet and they are $5k-$7k for just the turbo and a $1200 core like
YotaAtieToo said. Ordering parts online is also much harder as a DIY’er. Some stuff isn’t bad but other stuff you pretty much have to rely on your local dealer.
Here’s an invoice for a recent 20k mile PM on one of my Freightliner M2’s with 239k and no emissions work needed.