An interesting post this...I'll add my two bob's worth if I may?
Model subs, like any sort of model boat, are only as expensive as you wish them to be....to build a half decent surface boat will cost you what you want to spend on it. You want to build an all singing, all dancing warship with rotating deck guns, working lights, sound effects, and all the stuff that modellers like to put on their boats? I'll bet any of you that you can do it for well less than £100(excluding radio) My Tamiya Missouri cost me about £40, I think it was...it had rotating deck guns(a very simple modification using only a couple of bits of brass wire and a piece of plastic sheet)sound effects(dead easy, all you need is a small Mp3player and a small speaker under the deck...the Mp3 player I already had and the speaker came from a defunct radio)working lights(a couple of tiny leds I removed from an old tx and a battery case). Add to that the cost of a second hand 3-4 channel radio, two motors, couple of propshafts(brass wire inside brass tube)use the kit propellors, and you'll have plenty of change out of your £100 to go buy yourself a pint.
You want to build a nice fancy static diving submarine? No problems..apply the same rules as above. A Trumpeter Seawolf kit will cost you all of £20 odd, you don't need fancy acrylic tube for the WTC when there's plenty of plastic drainpipe tubing to be found in any skip you pass, and end caps can be bought from one or two of the lads on here, or(despite what people on here said about them)use coffee jar lids...with an application of silicone sealant they work a treat. Diving systems...now we need to spend some money. A second hand screenwash pump from a breakers yard will set you back all of a couple of quid, the ballast tank itself need be no more technical than a fizzy drink bottle(you fall over those as soon as you step out your front gate)and a few inches of tubing(which you would have got with the screenwash pump if you'd have asked nicely)
The technical bits...well, a second hand 4-channel radio will be more than sufficent, two microswitches for forward/astern and the same for the pump control...(let's call that £15 from ebay)you don't need fancy depth controllers, just learn to control it with your thumb....what else is there?
You don't need a workshop the size of an aircraft hangar, stuffed to bursting point with all the latest tools to make a working r/c model submarine, neither do you need a wallet the size of an Arab sheik's (I have neither, and I'll put money on the fact that any of the best model submariners in the country have either)so that's put that to bed nicely.
Some of the sub kits available are expensive, I'll agree....but then so are some of the surface boat kits. Take a look at the price of the top of range Deans Marine warship kit....frightening, isn't it? Take a look at the price of the Sheerline Akula sub kit...frightening, is'nt it? But...comparable! By the time you've shelled out the cost of a Deans marine warship kit and all the radio gear and electronics, by the time you've shelled out the cost of a Sheerline Akula and all the radio gear and electronics, I'll bet you there won't be more than a few quid difference in the two.
Back when I had my Engel Patrick Henry, my total outlay then was way over the £1000 mark, probably half as much again(and that was in the early '80's)the reason being that most of the stuff in that boat had to be designed and built for it, as nothing was readily available then as it is now. But you ask any of the guys who built and owned some of the big surface warships that turned up at the shows we used to go to, and cost was comparable even then.
My point is this...if you are in the fortunate postion of having a bottomless wallet you can own and operate the best that there is in model submarines, and the same goes for surface boats. If, like the majority of us on here, you have to go to work to pay your household bills, run the car, and still keep your marriage intact, then you won't have a bottomless wallet to play model boats with. The whole of the r/c hobby, be it boats, airplanes, helicopters, robots or cars is wholly dependant on money...your money. You can only spend what you have available to spend, so spend it wisely, and you can sail an r/c sub without fearing the knock on the door as the man comes to repossess your car/house/wife/whatever.
Rich