It's probably been suggested in the before, so my apologies to those that have seen and responded in the past.
At present the choice to complete/upgrade a building or cooldown period is set, I'd like to see it reduce as the time period reduces.
For example to skip cooldown on the spring park is 400 gems but that remains at 400 gems even if there is only 10 mins left.
I won't be alone in refusing to pay such a price, but I may well be tempted if it were just 5 gems. Can the price not reduce to reflect the period left?
I'm pretty sure I wouldn't be the only one tempted, so this would actually increase gem use/sales as no one is likely to pay the high cost of gems to complete buildings etc where as plenty of impatient players like myself will be lured into spending smaller amounts to skip the last mins/hours