Hyde said:
If the cost of a new ride is too high for what the park can afford, then it can't be built.
To expand on this, it's not always about absolute cost (i.e. the actual price tag of the coaster), but comparative cost plays a rather big role too. Comparative to what, you say? Building something else.
There will always be alternatives when considering what rides to invest in. This goes as far back as the concept stage (i.e. using a plot of land for a coaster, a kiddie area or a new restaurant), but also on the detail stage (say, if deciding on a thrill coaster, there's a choice between a B&M Invert or a Mack Launcher). The various alternatives will usually differ in price, maintenance costs and predicted draw of customers (translated into income, based on the attracted demographic and the amount of money they are expected to spend at the park).
Generally, a park will choose the option that brings in the greatest amount of income for the lowest price. Alternately, the option that brings in the most income per invested dollar. Any new acquisition will be measured against alternatives before the park decides what to build.
And therein lies the catch with Gigas. They present an enormous initial investment, but usually have a high return by drawing in loads of customers. However, if those crowds fail to turn up, a lot of money is lost. It's a relatively high risk project. What if, say, the coaster experiences downtime for months in its first season, where its marketability and crowd drawing potential is at the greatest? Loads of money lost. Their high "scariness factor" also means they are less attractive to families with kids, which traditionally are the greatest spenders at parks. If you want a sure return of investment, a smaller coaster is probably a safer bet. Less expenses, less pressure to draw huge crowds, and usually less prone to mechanical problems too.
Another factor that shouldn't be overlooked is space. A Giga will bind up a huge amount of space. The alternative to build a Giga on a plot of land, will usually be building two or more attractions/areas there over the span of several years. A Giga will have to justify its cost, not only in dollars and cents, but also in acres and square metres.
All in all, this means it isn't enough for a coaster to generate profit, it has to generate more profit than the alternative options. After all, why build a Giga for $30 million for a predicted income of $34 million, when, say, an Invert will cost $20 million and generate $23 million in revenue? Okay, you'll earn a million dollar less, but at a much smaller investment, and get more money back for each dollar invested. Besides, the land beside the Invert can probably be used for future developments, potentially giving you even more money. Or maybe you could even drop the coasters, invest $3 million in a kiddie area, and gain $5 million in income, still with loads of room to spare for next year.
Of course, probability, devaluing of money and lifecycle costs also have to be taken into account, but the gist of it stays the same. Namely, that the alternatives to building a Giga tend to make more sense economically.