I thought the Ozefridge units were fairly pricey but did not make any comparisons with other available kit systems.
If you purchase
the components and build it yourself you could probably budget
in the $1,000 - 1,200 range. The compressor
is the expensive bit for which you will pay $800 - 900 for a Danfoss or a lot less for a similar Chinese unit. The last time I went through the budgeting process I found that it was cheaper to buy a portable unit and pirate the parts
from it than to buy them as components.
Getting your hands on the gas is the big problem but if you are willing to use one of the hydrocarbon based refrigerants this is not a problem. According to the experts it is dangerous because it forms an explosive mixture with air but since most boats use the same gasses for cooking
and a refrigeration
system only has 100 grams or so of refrigerant and it is extremely unlikely that a leak would be big enough to provide sufficient gas to form a harmful mixture. In comparison to what could be created by a gas stove the risk associated with hydrocarbon refrigerant appears vanishingly small.
If you are the sort of person that loves a challenge and doing things yourself a possibility is that you buy a portable unit and use it whilst you clue up on refrigeration
and build your box then pirate it to do the boat frig installation