A COVID problem is still inventory, looks like cost now. When I did my panel I had to get some from Lowes, some from HD, Some from Amazon, and some from Canada Breakers. As no one had all I needed in stock or even the specific ones I needed. Prices in Canada were not too bad then.... I just looked at the costs here again, good thing I was sitting down!
If you require them (again verify this, they are pricey) plug on neutral is cheaper but it requires a special plug on neutral panel. With GFCI and/or CAFI the neutral and hot wire are connected to the breaker. Regular (old style) have a neutral pigtail on the breaker that then connects to the neutral bus (messy). Plug on breakers do not have the pigtail, instead there is a neutral bus and a hot bus they snap into. Cleaner panel (no pigtails), faster and they are cheaper! If I was doing it again today, plug on all the way.
Looking at pricing, I paid around $80 (CAFI only) to $120 (DF GFCI/CAFI) for a pigtail (not plug-on) breakers, some 15 amps some 20 amps. HD has the 15A DF for $180 CDN now (plug on is $120)! The HD cost in the US is $64 USD!!!!