Corny kegs really aren't that expensive. You can get a reconditioned Grade A for £57 delivered. The disconnects I got were £1.60 each. 6.35kg gas bottle cost me £18.99. Couple of john guest fittings and a party tap, call it £90 - but after that you're just including the cost of a keg each time.
Plastic pressure barrels - if you manage to get one of the better ones that left the factory not already on fire then it's how many brews until it ruins a batch of beer? Two, three?
You need to use sugar to prime it which costs you extra conditioning time and wastes beer. Of course you get the bonus of those lovely vitamin fortified final pints that you'd better drink on a Friday or Saturday because your guts certainly won't handle a commute, oh no no no. Or you could just consider it a sacrifice to the demon that comes free inside every pressure barrel.
Those little sparklet bulbs to top up that - let's face it : flaccid beer - £4.50 for 80g of gas. Let's see, how much would that work out to for the same I get in my £18.99 cylinder... oh £357.19.
And those replacement rubbers for the s30, a mere snip at £4.95 a set. Hope they're not a horror to put on. Certainly haven't stabbed myself or everyone else in the vicinity with screwdrivers trying to get them on and off. No sir-eeee! How much for a set of corny replacements? Oh £1.60 - or 3 sets delivered for £5.99. I haven't managed to stab anyone with the little spanner used to take off the posts yet. I've tried, mind.
And. Someone comes round your house and you say "Do you want to try some of my beer?" (Don't say homebrew, not yet). You lead them into the place wherever it is your wife lets you keep your barrel and they go "Oh, my dad had one of them. He still wakes up screaming sometimes." You open up that white plastic tap and out comes that lovely, lovely gushing frothing sputtering seething pint of foam. Keep smiling, bit of eye contact to assure them it's ok. "It'll settle in a minute..." Yay! Fifteen minutes later they've got a whole 8mm of beer.
Somebody comes round and you show them a corny keg and they think you're selling secrets to the Russians and wonder what lever in the room opens a secret panel or starts the elevator to your underground bunker.
It's your choice, of course. I wouldn't want to influence you.