Who is "SalesForce"? The Merchant Account place? If they don't know JavaScript it may be time to look for another CC processor.
Actually, you're using JQuery -- not "pure" JavaScript. And I can create a script to do that math and drop it into the page in about 3 lines of "pure" JavaScript; no JQuery necessary. The problem may be how your form handling script interacts with that.
Ancillary to that is the fact that your potential users can change the "cost/item" field from $175 to whatever they want. Scary? How would you like 100 people buying what should be $175 tickets for $1.75 each? Cuts into the night's gross (and net) doesn't it? Might be possible with your current code. If it were me I'd change
<input name="UnitPrice1" type="[B][COLOR="#FF0000"]text[/COLOR][/B]" id="UnitPrice1" value="175" size="7" />
to:
<input name="UnitPrice1" type="[B][COLOR="#FF0000"]hidden[/COLOR][/B]" id="UnitPrice1" value="175" />
Then change
<span class="questions">I would like to buy tickets to the 35th Anniversary Party at
<input name="UnitPrice1" type="text" id="UnitPrice1" value="175" size="7" />
per ticket </span>
to:
<span class="questions">I would like to buy tickets to the 35th Anniversary Party at $175.00 per ticket </span>
Just sayin'...