Picture a number standing on the bottom step of a staircase. It is where the money talk begins, and every step after it goes up: an extra feature, another bid, a bigger final bill. A starting price never tells you what will be paid in the end. It only tells you where the counting starts.
From the picture
賽馬開跑那一刻定下的賠率
英國賽馬用 price 來講賠率，不是講錢。開跑那一刻固定下來、之後拿來結算的那個數字，就是這條線上的「起點價」——時間一到，一切從這個數字開始算。
noun · C1
In British English, the odds on a horse or dog that are fixed at the moment the race starts, and that are used to work out what a bet pays when no other odds were agreed. In race results it is usually written SP.
（賽馬）起跑賠率
noun · B1
The lowest price a kind of thing is sold at, for the plain version with nothing extra added; also the lowest price a seller is willing to take for something they are selling.
起價／底價
noun · B2
At an auction, the price the bidding begins at. Offers only go up from that number, so the thing usually sells for more than it.
起標價