WIFI onboard for less than $100USD. Or how I was having it for over 3 years already.
 Of course you need to find open access point while you are anchored or to go to a bar with strong signal and to get a beer. There are also paid hotspots specifically dedicated to cruisers.
 And I am a software engineer by profession so making it work is not hard for me.
 But in my opinion is dead easy.

I got TP-Link CPE210 and CPE510 (It is nice to switch between 2.4GHz and 5GHz). Both of them cost lest than $50USD each on Amazon.
 Those are directional antennas and are a lot stronger than omni directionals. Though you might loose singal when you are swinging a lot, but it is unlickly that you will have better access with latter. (Previously I wrote about my previousTP-Link TL-WA7210N which is old and is based on 12V source power).
 Current ones require 24V and most likely you got 12V battery bank so DC-DC 12V to 24V converter is required which starts from $8.80USD. And you should put 1A fuse infront of it just in case.

Third thing you need is Power over ethernet (PoE) injector. Which costs about $20USD. That is the one I got. As WIFI repeaters come with AC power adapters only and you don't want to use your inverter all the time.

Then you buy long enough ethernet cable so that you could mount TP-link outside and to link it with PoE inside.

TP-Link has it's own WIFI access point, you just neet to read the manual how to handle it.
 Which I don't use because I have Raspberry Pi and I forward TP-links through it. Thats what I use another short ethernet cable for. But I would not recommend it to a person who has no experience dealing with IT networking.

Another thing I'd like to moan about is that every gadget like Iridium GO! has it's own WIFI access point so you can't mount it to your existing network via cable. You have to switch between WIFI on your phone or laptop.

How much do you need to pay for your marine grade WIFI stuff?