Ki Tisa: Half of it is 250, or Half as Much, that is, 250

To see the trup chart larger and better (since it is scaled down in this post), please click on the image.

Shadal:

[ כג ] כפי הטעמים , וכדעת הירושלמי שקלים ריש פרק ששי ( הלכה א ') .

The pasuk:

כב וַיְדַבֵּר ה, אֶל-מֹשֶׁה לֵּאמֹר.	22 Moreover the LORD spoke unto Moses, saying:
כג וְאַתָּה קַח-לְךָ, בְּשָׂמִים רֹאשׁ, מָר-דְּרוֹר חֲמֵשׁ מֵאוֹת, וְקִנְּמָן-בֶּשֶׂם מַחֲצִיתוֹ חֲמִשִּׁים וּמָאתָיִם; וּקְנֵה-בֹשֶׂם, חֲמִשִּׁים וּמָאתָיִם.	23 'Take thou also unto thee the chief spices, of flowing myrrh five hundred shekels, and of sweet cinnamon half so much, even two hundred and fifty, and of sweet calamus two hundred and fifty,
כד וְקִדָּה, חֲמֵשׁ מֵאוֹת בְּשֶׁקֶל הַקֹּדֶשׁ; וְשֶׁמֶן זַיִת, הִין.	24 and of cassia five hundred, after the shekel of the sanctuary, and of olive oil a hin.

The Yerushalmi (Shekalim 24b) in question states:

שמות ל) ואתה קח לך וגו' וקידה חמש מאות וגו' שהן אלף וחמש מאות מנים:

That is, it sums it up to 1500, which is does as:
flowing myrrh as 500,
cinnamon as 250,
calamus as 250
cassia as 500.
The sum of this is 1500.

Here is the trup:

וְאַתָּ֣ה קַח־לְךָ֮ בְּשָׂמִ֣ים רֹאשׁ֒ מָר־דְּרוֹר֙ חֲמֵ֣שׁ מֵא֔וֹת וְקִנְּמָן־בֶּ֥שֶׂם מַֽחֲצִית֖וֹ חֲמִשִּׁ֣ים וּמָאתָ֑יִם וּקְנֵה־בֹ֖שֶׂם חֲמִשִּׁ֥ים וּמָאתָֽיִם׃

Thus trup accords with this because it puts together וְקִנְּמָן-בֶּשֶׂם מַחֲצִיתוֹ on one side of a disjunctive accent and חֲמִשִּׁים וּמָאתָיִם on the other side, such that it is to be interpreted as half as much as the mor deror which was 500, and thus 250.

Rashi, meanwhile, offers an interpretation in accordance with the Bavli, and against the Yerushalmi and the trup:

half of it two hundred and fifty [shekel weights] Half of the amount to be brought shall be two hundred and fifty; thus altogether it is five hundred [shekel weights], like the amount of pure myrrh. If so, why was it stated in halves? This is a Scriptural decree to bring it in halves to add to it two overweights, because we do not weigh [the spices] exactly. So it was taught in Kereithoth (5a).

Shadal feels that if this was the meaning, there should not be a disjunctive accent of tipcha on the word machatzito. Rather, presumably the disjunctive accent would be one word earlier (and would appear as a zakef, because of its distance from the etnachta), such that it would be:

וְקִנְּמָן-בֶּשֶׂם || מַחֲצִיתוֹ חֲמִשִּׁים וּמָאתָיִם.

In earlier posts (see here and here), I translated Shadal's Vikuach al Chochmat haKabbalah, where he attempts to prove things about the age of trup and whether the nakdanim were willing to argue with gemaras, from sources such as these. When it comes down to it, we see that in this case he decides in favor of the Yerushalmi and the trup.