What is the ruling if a potential claimant of pre-emption states they do not know the price paid by the buyer?

Primary text

The statement of the potential claimant of pre-emption (Shuf'ah) asserting ignorance of the purchase price is accepted, and their assertion stands. This is permissible because the claim is possible; the buyer may have purchased the property in bulk (juzāfan) or forgotten the exact price paid. The claimant must swear an oath regarding this ignorance. Upon taking the oath, the right of pre-emption lapses because it cannot be established without the claimant offering the actual price paid, and the seller cannot be compelled to accept a sum other than what the buyer claims to have paid.