I worked for an arborist for five years. I was literally a tree hugger by profession. Especially on those tall skinny ones. Seems like you got a damn good deal on the removal, but I have not seen the trees, the amount of brush they made, the log load, or the buildings they may have been next two.
We charged about about $1000 per day which included 24 man hours labor (three workers) plus insurance and cost of material
I have seen one tree cost $1500 and six cost $500. It all depends.
I would only tip the guys if they really tried to do something extra for you. Stuff that is not spelled out in the contract. Like offer you the wood if it came from a decent tree and stack it up for you where you wanted etc.
My crew pruned a 500 year old oak for a lady who was a great-grandmother. Her kids who were in their 60's-70's got together and paid for the job for their mom. They made a picnic of it and sat on the porch and watched with interest and compliments on our progress. They took pics of the job and even insisted they feed us lunch from their BBQ pit. We went the extra mile and did a Class 1 (National Arbor Society designation for type of work) prune job on that tree that was not in the contract. In this case, a tip is welcome, but not expected. We just wanted to do right by these good people and the tree was deserving of it also.
We each got a 5 dollar tip for beer that evening.
My story and two cents.