As for all technical products: a rough estimate of a price can not be trimmed down to 'acceptable acuracy' if you do not either wish to be far more specific or accept a 1:10 factor as accurate eneough.
Sizes and pressure class would help, but a lot of other factors will influence the price (certifications and test required, materials for valves and trim, type of PSV (spring operated, lifting construction, pilot operated, capacity (not pipesize) will determin PSV- size, quality, local market and pricing, one or twenty pcs etc. etc.
Advice: ask a vendor. I have often given pre-prices, without binding as project calculation prices, based on our own products and bound to the technical details given from our and customers side.