It costs $45 to have the battery changed and the watch pressure tested. If you buy a watch that costs less than $45 and it lasts you a year then you are ahead.
Cheap is also good because the bands are only as strong as the $1 pin that holds the band together. It gets a bit tedious diving for your $800 watch because a $1 pin has broken.

Tide calculators are a bit of a waste of time. They just do a simple arithmetic calculation based on a 50 minute difference in the tides. It's more complicated than that. They're ok if you set it at the start of a trip and use it for just a few days. Eventually you have to reset it. It's much easier to print the tides out for each trip away or load it into your phone or access on the smart phone. On a daily basis it's easy enough to just remember the tide times.
A digital tide time display is better than a dial or a graph if you are after accuracy. The graphs and dials can only be read down to about 2-3 hours precision.
I have a Casio G-Shock solar powered jobbie for flying trips (to the Himalayas) and it is a good thing. Mega cheap on ebay. They're $450 in the shops and I got mine for $120. It's too thick for surfing. It barely fits under the wetsuit. Thick watches can break your wrist if you hit them wrong.
I use a relatively cheap Rip Curl watch for surfing that I got for my birthday. It's nice and slim and doesn't get in the way.
If I was buying a watch I'd buy a $20 ebay Casio.