I was having a look at hive Engine, and the voucher price has already spiked up to over $20.

This is incredible, the new packs will essentially cost $4USD and $20USD voucher.

What will a gold promo card cost.

You will need to purchase 1000 packs to get a guaranteed gold promo. So that means you need to spend $24,000 to get a gold promo card! phenomenal!

Will the price go down?

It's anybody's guess if the price will go down or not, and splinterlands may have a challenge on their hands, on how to retain the value, of the cards etc, when vouchers are not required... so watch this space I expect them to consider using vouchers for much longer.

SPS price

Given that 140 staked SPS will generate 1 voucher. at a price of $0.90, and a voucher price of $20, this means that the return is 15% per month, which is almost 200% APR

Will the SPS rise to reduce the yield? who knows.. its exciting to watch this play out.

I'll post a longer analysis, once more data is available..in the meantime happy voucher hunting!