A few years ago expansions were about 1/2 the original cost. So if you estimate the cost of the "original" to be about £40 (which will be reduced by generic retail factoring to be about £35) then you might expect to pay about £20 (reduced to £19.99), per expansion.
So, you'd need the original plus 2.3 expansions to cost more than the £80 kickstart.
These days most "expansions" seem to be released as a new game, costing the same as the original, even if they are direct addons and not a new engine. (just look at starcraft2 if you want an example).
So you'd need the original and 1.3 expansions to cost more than the kickstart.
DLC tends to operate as extra bits, not normally a huge revamp of the game. Some companies do use it to release expansions, but again it tends to work out at the standard expansion cost.
Overall it can also cost more to download a "lot of bits" than 1 large change.
Of course the game could be a total flop, destroying the company and never having an expansion made.
If anyone actually thinks that this will be the case, i strongly recommend that they don't buy the game.
I'm working on the simple principle that i loved the original and the next one and kind of the last one. So i'm buying the game and if there are only 2 expansions in the next 4 years then i've not "lost" any money. If there are more, then i've saved a lot
Besides, i expect the game to save me a lot of money. Mainly from a reduced pub-based alcohol intake!