Oyster Card Question

Hi All
So I've just started a new job and will be working 2 days a week in London. I'm trying to figure out whether it will be worth getting an Oyster Card and I just want some clarification on what I think is correct is actually correct.....

So for me to get a one day travel card from Hemel is £22.40 but a return to Euston is only £16.80. So assuming I only go straight to and from the office (in Victoria), it should be £1.90 each way from Euston (is this correct?) therefore being a total price of £20.60.

Have I got this right? Are there any hidden costs I should know about?

Thanks!!!!!

That looks like you got it right. Doing pay as you go Oyster much more economical if you're not regularly using London transport. You're best off doing the way you've calculated (return to Euston + 2 single tube journeys).

By the way: hello neighbour! I'm in Harpenden, just down the road from you. 

Ah thanks very much! Just wanted to make sure that I wasn't going crazy!

And hellooooooooo neighbour! I love Harpenden, its a lovely little town! My dad works there and it's where my orthodontist was based hehe How are you liking it?

Harpenden is a wonderful place to live! It just has the worst train service in the world, which might be overlooked if I weren't relying on it every day!

I've not been to Hemel yet. My BF only just recently bought a car (we had previously been living in London), so we're slowly exploring the area not connected by the train. Anything worth visiting there?