Have you notice the cost of lumber has gone up 20 percent

One way around pricing a job so you don't end up on the losing end is to bid it as a break down of everything. Make sure you get paid what your time is worth but make sure the customer knows he is responsible for the costs of supplies and materials and that if they decide to make changes after they give you the go-ahead it will cost more.

Bid your labor cost for what it will take to pick up materials, build and finish the project, and deliver it to the customer. I give a not to exceed cost (if you underbid the labor then it is your fault, make sure you cover everything in your labor cost). You also need to add a note for any changes to the original design as bid.
Bid any hardware, finish, and other supplies at cost plus shipping, taxes, and fees. Possibly add a small fee for research and ordering time, this fee can also help cover any price increases.
Bid other materials like wood as "approximately xxx BF of (wood-type) @ $x.xx per BF, = $xxx.xx, actually cost depend on price when purchased".
Also, add a flat rate charge for misc. supplies like shop towels, glue, brushes, screws, fasteners, and any specialty items like mixing cups and stir sticks for epoxies

Example:

Labor: not to exceed 982.42 to build, finish, deliver
Hardware: 72.65 plus any shipping, taxes, and fees
Wood: approximately 115 BF of Red Oak @ $5.45 per BF, = $626.75, actually cost depends on price at time of purchased plus any taxes and fees
Finish: 63.28 plus any shipping, taxes, and fees
Misc supplies: 25.00 for misc supplies -glue, towels, brushes

NOTE: These costs are for the project as designed - any changes will be at additional cost)

Lumber mills technically weren't shut down

I work for west fraser. Alberta plywood specifically. We were deemed an essential service (i believe the whole forrestry industry was) as we are a supplier for home depot. If your in Ontario or Quebec buying sheating good chance I helped dry the veneer in that piece.

We were curtailed for 6 weeks ONLY because we couldn't sell the plywood when Ontario and Quebec shuttered their construction industry. We were full. To the brim no Where's to put the plywood of they wanted to.

During the 6 week shut down 3 weeks we ran at half capacity. To fill home depot orders.

These companies would sooner leave the trees on the ground and me at home without a job if they weren't making money.

Commodities will always make money. They cut production until demand ramps up. 100 percent though if there isn't new houses going up the mills will need to shut down.

I'd be very worried about a lot of the small to medium size mills not surviving covid 19, and having the big forestry companies being able to charge more less competition.