You only meed MOT20 for iui for ivf/icsi you need MOT5 or 10 X
Are you with the NHS or a private clinic? IUI uses motility 20+ motility because it requires good motility to ensure the sperm travels up when inseminated. Where are as IVF/ICSI the sperm is placed close to the egg or injected directly in to the egg so motility does not need to be so high. If you are doing IVF/ICSI you do not need 20+.
Assuming it’s similar to US banks, the amounts available to purchase and options are different for each donor, so I think it may just depend on how much that person donated and how it was prepared(frozen)