Based on the raw numbers, should be a roughly 60% gap between the RX5700 and RX5500, also half the memory.
That would put it right around the GTX1660 / RX590 in terms of relative performance, which is roughly $190 with the GTX1660 Super sitting at $220 or so. Best case, MSRP of $180 with sales and discounts putting it around there, unless Nvidia discounts the 1660 with the 1660 Super now in the same price bracket, assuming that price is feasible anyway.
In other words, A high end 580 or decent 590 will do just fine right this moment without leaving much to be desired.