And now, real-time sample splicing
Now, Stan can say any possible value up to 10950 pieces of eight. The existing samples are still use of course. The splicing script is only called for those cases where no pre-recorded sample exists.
And I think, it is a bug that the porthole defogger has no price. I set it to 450, like all the other extras. Not only are some samples recorded under the assumptions that each extra costs 450, there is also this line by Stan in every version of the game: "TWO THOUSAND LOUSY PIECES OF EIGHT!?!". With the ability to reduce the price a further 450 by not taking the porthole defogger, it is actually possible to get the ship for 2000. The existence of that line make me think, that it was the actual intention to begin with. Plus, it doesn't seem like Stan to give that for free.
The only restriction I have still in place when voice-only-mode is used: Your first offer can not be higher then 3000. Once you said your first offer, all options are available again, like it was in the original game.
Although this splicing script requires a bunch of print instructions to be executed in order to form the sentence, I managed to have the '.'-key usable to skip the line in its entirety.